Virtual Exploration of Safe Entry Zones in the Brainstem: Comprehensive Definition and Analysis of the Operative Approach

BACKGROUND

A detailed and accurate understanding of the intrinsic brainstem anatomy and the interrelationship between its internal tracts and nuclei and external landmarks is of paramount importance for safe and effective brainstem surgery. Using anatomical models can be an important step in increasing such understanding. In the present study, we have shown the applicability of our developed virtual 3-dimensional (3D) model in depicting the safe entry zones (SEZs) to the brainstem.

METHODS

Accurate 3D virtual models of brainstem elements were created using high-resolution magnetic resonance imaging and computed tomography to depict the brainstem SEZs.

RESULTS

All the described SEZs to different parts of the brainstem were successfully depicted using our 3D virtual models.

CONCLUSIONS

The virtual models provide an immersive experience of brainstem anatomy, allowing users to understand the intricacies of the microdissection that is necessary to appropriately work through the brainstem nuclei and tracts toward a particular target. The models provide an unparalleled learning environment to understand the SEZs into the brainstem that can be used for training and research.

Emergency surgery for brainstem cavernoma haemorrhage with severe neurological presentation. Is it indicated and worthwhile?

Background: Brainstem Cavernoma (BSCM) haemorrhage is a complex condition, especially when patients present rapid neurological deterioration. Traditionally, these patients were initially treated by non-interventional means. Surgery was generally reserved for cases who presented a 'benign' evolution in a subacute/delayed fashion. Timing of surgery remains controversial. Since rebleeding is frequent and carries a high mortality, many of these patients do not tolerate this approach. Urgent/emergent surgery may be indicated and lifesaving.Methods: A single center experience is reported in which an aggressive approach was used with urgent/emergency surgery carried out on patients with BSCM haemorrhage and rapid neurological deterioration, ventilatory impairment and/or coma. A review of 5 consecutive cases where urgent/emergent surgery was performed is presented. The pre-operative status, pre- and post-operative examinations, surgical approach and neurological residual deficits/outcomes are reported.Results: Four females and one male with ages ranging from 36 to 66 years with rapid neurological deterioration, ventilatory impairment and/or coma were operated between 2011 and 2018. Favourable outcomes were observed with a modified Rankin Scale varying from 1 to 4. Cranial nerve deficits as well as motor and sensitive deficits were observed but all the patients recovered cognitive integrity.Conclusions: Our small series reveals an acceptable outcome with ultra-early surgery. This approach appears to be a valid option when there is rapid neurological deterioration, respiratory impairment and/or early onset coma. However, further studies are required to elucidate the optimal strategy.

Surgical management of symptomatic brain stem cavernoma in a developing country: technical difficulties and outcome

Brain stem cavernomas (BSCs) are angiographically occult vascular malformations in an intricate location. Surgical excision of symptomatic BSCs represents a neurosurgical challenge especially in developing countries. We reviewed the clinical data and surgical outcome of 24 consecutive cases surgically treated for brain stem cavernoma at the Neurosurgery Department, Alexandria University, between 2006 and 2014. All patients were followed up for at least 12 months after surgery and the mean follow-up period was 45 months. All patients suffered from at least two clinically significant hemorrhagic episodes before surgery. There were 10 males and 14 females. The mean age was 34 years (range 12 to 58 years). Fourteen cases had pontine cavernomas, 7 cases had midbrain cavernomas, and in 3 cases, the lesion was found in the medulla oblongata. The most commonly used approach in this series was the midline suboccipital approach with or without telovelar exposure (9 cases). There was a single postoperative mortality in this series due to pneumonia. Fourteen cases (58.3 %) showed initial worsening of their preoperative neurological status, most of which was transient and only three patients had permanent new deficits and one case had a permanent worsening of her preoperatively existing hemiparesis. There was neither immediate nor long-term rebleeding in any of our cases. In spite of the significant associated risks, surgery for BSCs in properly selected patients can have favorable outcomes in most cases. Surgery markedly improves the risk of rebleeding and should be considered in patients with accessible lesions.

Use of Actuator-Driven Pulsed Water Jet in Brain and Spinal Cord Cavernous Malformations Resection

BACKGROUND

A piezo actuator-driven pulsed water jet (ADPJ) system is a novel surgical instrument that enables dissection of tissue without thermal damage. It can potentially resect intra-axial lesions while preserving neurological function.

OBJECTIVE

To report our first experience of applying an ADPJ system to brain and spinal cord cavernous malformations.

METHODS

Four patients (2 women and 2 men, mean age 44.5 years) with brain (n = 3) and spinal cord (n = 1) cavernous malformations were enrolled in the study. All surgeries were performed with the aid of the ADPJ system. Postoperative neurological function and radiological findings were evaluated.

RESULTS

The ADPJ system was useful in dissecting boundaries between the lesion and surrounding brain/spinal cord tissues. The pulsed water jet provided a clear surgical view and helped surgeons follow the margins. Water jet dissection peeled off the brain and spinal cord tissues from the lesion wall. Surrounding gliotic tissue was preserved. As a consequence, the cavernous malformations were successfully removed. Postoperative magnetic resonance imaging confirmed total removal of lesions in all cases. Preoperative neurological symptoms completely resolved in 2 patients. The others experienced partial recovery. No patients developed new postoperative neurological deficits; facial palsy temporarily worsened in 1 patient who underwent a suprafacial colliculus approach for the brainstem lesion.

CONCLUSION

The ADPJ provided a clear surgical field and enabled surgeons to dissect boundaries between lesions and surrounding brain and spinal cord gliotic tissue. The ADPJ system is a feasible option for cavernous malformation surgery, enabling successful tumor removal and preservation of neurological function.

Pathological response of cavernous malformations following radiosurgery

OBJECT

Stereotactic radiosurgery (SRS) is a therapeutic option for repeatedly hemorrhagic cavernous malformations (CMs) located in areas deemed to be high risk for resection. During the latency period of 2 or more years after SRS, recurrent hemorrhage remains a persistent risk until the obliterative process has finished. The pathological response to SRS has been studied in relatively few patients. The authors of the present study aimed to gain insight into the effect of SRS on CM and to propose possible mechanisms leading to recurrent hemorrhages following SRS.

METHODS

During a 13-year interval between 2001 and 2013, bleeding recurred in 9 patients with CMs that had been treated using Gamma Knife surgery at the authors' institution. Microsurgical removal was subsequently performed in 5 of these patients, who had recurrent hemorrhages between 4 months and 7 years after SRS. Specimens from 4 patients were available for analysis and used for this report.

RESULTS

Histopathological analysis demonstrated that vascular sclerosis develops as early as 4 months after SRS. In the samples from 2 to 7 years after SRS, sclerotic vessels were prominent, but there were also vessels with incomplete sclerosis as well as some foci of neovascularization.

CONCLUSIONS

Recurrent bleeding after SRS for CM could be related to incomplete sclerosis of the vessels, but neovascularization may also play a role.

Symptomatic cavernous malformations of the brainstem: functional outcome after microsurgical resection

Brainstem cavernous malformations are associated with a considerable risk of hemorrhage and subsequent morbidity. This study provides a detailed work-up of clinical and radiological outcome as well as identification of prognostic factors in patients who had suffered from symptomatic hemorrhages. Patients who had undergone surgery of symptomatic BSCMs were evaluated pre- and postoperatively both neurologically and neuroradiologically supplemented by telephone interviews. Additionally, patients were scored according to the Scandinavian Stroke Scale. Multiple uni- and multivariate analyses of possible clinical and radiological prognostic factors were conducted. The study population comprised 35 patients. Mean age at operation was 39.3 ± 13.0 years with microsurgical resection of a total of 37 different BSCMs between 2002 and 2011. Median clinical follow-up was 44.0 months (range 8-116 months). Postoperative MRI showed eventually complete resection of all BSCMs. Postoperative overall outcome revealed complete resolution of neurological symptoms for 5/35 patients, 14/35 improved and 9/35 remained unchanged. 7/35 suffered from a postoperative new and permanent neurological deficit, mostly affecting the facial nerve or hemipareses with mild impairment. Pre- and postoperative Scandinavian Stroke Scale scores were 11.0 ± 2.4 and 11.4 ± 2.2 (p = 0.55). None of the analyzed factors were found to significantly correlate with patients' clinical outcome. Complete resection of brainstem cavernous malformations can be achieved with an acceptable risk for long-term morbidity and surgery-related new deficits (~20 %). Neurological outcome is mainly determined within the first 6 months after surgery. Surgical treatment of brainstem cavernous malformations is recommended in symptomatic patients, in whom the lesion is accessible for surgery.

Effective surgical treatment of cerebral cavernous malformations: a multicenter study of 79 pediatric patients

OBJECT

Cerebral cavernous malformations (CCMs) are common vascular lesions in the brain, affecting approximately 0.5% of the population and representing 10%-20% of all cerebral vascular lesions. One-quarter of all CCMs affect pediatric patients, and CCMs are reported as one of the main causes of brain hemorrhage in this age group. Symptoms include epileptic seizures, headache, and focal neurological deficits. Patients with symptomatic CCMs can be treated either conservatively or with resection if lesions cause medically refractory epilepsy or other persistent symptoms.

METHODS

The authors retrospectively analyzed 79 pediatric patients (41 boys and 38 girls) from 3 different centers, who were surgically treated for their symptomatic CCMs between 1974 and 2004. The mean age of the children at first manifestation was 9.7 years, and the mean age at operation was 11.3 years. The main goal was to compare the clinical outcomes with respect to the location of the lesion of children who preoperatively suffered from epileptic seizures.

RESULTS

Of these patients, 77.3% were seizure free (Engel Class I) after the resection of the CCM. Significant differences in the outcome between children who harbored CCMs at different locations were not found.

CONCLUSIONS

Resection seems to be the favorable treatment of symptomatic CCMs not only in adults but also in children.

Surgical strategies in treating brainstem cavernous malformations

BACKGROUND

Optimal therapy of brainstem cavernous malformations (BSCMs) remains controversial because their biological behavior is unpredictable and surgical removal is challenging.

OBJECTIVE

To analyze our experience with BSCMs and to conduct a review of the literature to identify a rational approach to the management of these lesions.

METHODS

Fifty-five patients harboring 57 BSCMs underwent surgery and 17 patients were treated conservatively during the 10-year period from 1999 to 2008. The operative strategy was to perform complete CM resection and to preserve any associated venous malformation with minimal functional brainstem tissue sacrificed. The National Institutes of Health Strength Scale (NIHSS) was used to assess neurological status.

RESULTS

The average hemorrhagic and rehemorrhagic rates were 4.7% and 32.7% per patient-year, respectively. Total lesional resection was achieved in all operated patients. Their mean NIHSS score was 4.6 after the first episode, 3.5 preoperatively, 3.2 at discharge, and 1.4 after a mean follow-up of 49 months. Complete recovery rates of motor deficits and sensory disturbances from the preoperative state were 70.4% and 51.7%, respectively. Complete recovery rates for cranial nerves III, V, VI, and VII and the lower group were 60%, 63.2%, 25%, 57.1%, and 80%, respectively. For the conservative patients, the mean NIHSS score was 5.9 after the first episode and 1.7 after a mean follow-up of 40 months.

CONCLUSION

NIHSS is optimal for evaluating the natural history and surgical effect of patients harboring BSCMs. Surgical resection remains the primary therapeutic option after careful patient screening and preoperative planning.

Surgical management of brainstem cavernous malformations

Bleeding from brainstem cavernomas may cause severe deficits due to the absence of non-eloquent nervous tissue and the presence of several ascending and descending white matter tracts and nerve nuclei. Surgical removal of these lesions presents a challenge to the most surgeons. The authors present their experience with the surgical treatment of 43 patients with brainstem cavernomas. Important aspects of microsurgical anatomy are reviewed. The surgical management, with special focus on new intraoperative technologies as well as controversies on indications and timing of surgery are presented. According to several published studies the outcome of brainstem cavernomas treated conservatively is poor. In our experience, surgical resection remains the treatment of choice if there was previous hemorrhage and the lesion reaches the surface of brainstem. These procedures should be performed by experienced neurosurgeons in referral centers employing all the currently available technology.

Operative management of brainstem cavernous malformations

Brainstem cavernous malformations (CMs) are complex lesions associated with hemorrhage and neurological deficit. In this review, the authors describe the anatomical nuances relating to the operative techniques for these challenging lesions. The resection of brainstem CMs in properly selected patients has been demonstrated to reduce the risk of rehemorrhage and can be achieved relatively safely in experienced hands.

Surgical strategy for insular cavernomas

PURPOSE

Surgical treatment of cavernomas arising in the insula (especially in dominant cerebral hemisphere) is challenging in reason of the proximity to the internal capsule and lenticulostriate arteries. The advent of image guidance systems and intraoperative mapping of the subcortical language pathways has broadened the surgical indications for these lesions. In this work, we report four cases of insular cavernomas operated on, and we define a surgical strategy for these lesions.

METHODS

Between July 1997 and May 2007 in our department, four patients harboring an insular cavernoma were operated on by using image guidance system (neuronavigation in three cases, ultrasound in one case). Subcortical stimulations were used to preserve the functional language area in one case.

FINDINGS

The image guidance system determined the exact planning of the approach and determination of the ideal trajectory of insular cortex dissection. In a case of a deep left insular cavernoma, the shortest approach to remove the cavernoma was stopped in per-operative time because subcortical stimulation produced a speech inhibition, justifying another insular corticotomy. No surgical complications occurred, and the postoperative course was uneventful in all patients.

CONCLUSION

As it has been proposed by many authors, image guidance system is recommended in surgery of insular cavernomas. When the lesion is located in the dominant hemisphere, intraoperative mapping of the subcortical language pathways is also indicated to preserve the language functional areas.

Brain stem cavernous malformations

We retrospectively reviewed the clinical experience of 30 patients with brain stem cavernous malformations (BSCM) treated operatively and non-operatively at our hospital between 1983 and 2005 to elucidate the natural history of BSCM and the factors that affect surgical outcome. Inpatient charts, imaging studies, operative records, and follow-up results were evaluated. The average follow up was 48.5 months. Twenty-two patients (73.3%) received surgical extirpation and of these 86.4% improved or stabilized and 13.6% deteriorated with permanent or severe morbidity. There was no mortality. Size, preoperative status, and surgical timing were factors related to surgical outcome. In the non-operative group, 50% of the patients were the same or better, 25% deteriorated, and 25% died. With appropriate patient selection, resection of BSCM can be achieved with acceptable morbidity compared with the ominous natural history of these lesions.

Does conservative management for brain stem cavernomas have better long-term outcome?

There has been a controversy in the last 15 years on the correct management of brain stem cavernomas. We have reviewed our experience of the last 10 years in a single Institution and reviewed related literature published in the last 15 years. We recorded the demographics, clinical presentation, rebleeding episodes, incidence of neurological events and outcome assessed by recording the change of the modified Rankin scale in 21 cases. Univariate analysis was applied to test the effect of demographics, and presentation on the incidence and timing of rebleeding, chance of having a new neurological event, the number of subsequent neurological events and outcomes. Six cases were treated with surgery and 15 cases were managed conservatively. We obtained follow-up data in 20 patients (95%). Mean follow-up period was 79.7 months (range: 6-244, median 70 months). There were 0.05 rebleeding events per patient-year and 0.1 episodes of neurological deterioration per patient-year. No mortality was noted in either the surgical or the non-surgical group. Three of the six surgical cases had a reoperation. The outcome was improved in one patient, unchanged in 1, and worse in 3 surgical patients. In the case of conservative management the outcome was improved in two patients, unchanged in five patients, and worse in eight patients. Outcome was worse in the case of multiple cavernomas (p = 0.012). Our findings suggest that conservative management may be appropriate in individual cases when compared with surgery, but this difference was not statistically significant enough in order to support a change in practice. The natural history of brain stem cavernomas appears more benign than previously thought.

Cavernous angiomas of the brain stem and spinal cord

This article reviews the pathology, clinical course and management of cavernous angiomas in the brain stem and spinal cord. Both lesions have been diagnosed with increasing frequency as a result of magnetic resonance image scanning. Brain stem lesions tend to present dramatically; their treatment remains microsurgical excision despite some studies that have looked at the use of radiosurgery. Spinal lesions are either extra-, or more commonly, intramedullary. Intramedullary cavernomas present with a wide spectrum of symptoms ranging from acute haematomyelia to presentations that mimic demylelinating conditions; extramedullary cavernous angiomas tend to produce radicular symptoms or subarachnoid haemorrhage. Both are treated by microsurgical excision.

Comparative Analysis of the Retrosigmoid and Lateral Supracerebellar Infratentorial Approaches along the Lateral Surface of the Pontomesencephalic Junction: A Different Perspective

Objective:

To quantitatively assess the working distance and angle of attack among the retrosigmoid (RS), lateral supracerebellar (LS), and extreme lateral supracerebellar (EL) views on the lateral surface of the pontomesencephalic junction.

Methods:

Eight sides of silicone-injected fixed cadaveric heads were dissected using the three approaches. All predetermined anatomic points were collected by use of a frameless stereotactic device. The length of exposure and the angle of attack were calculated and compared. Predissection imaging was obtained for illustration.

Results:

The LS and EL approaches created a horizontal working space as compared with the vertical working space created by the RS approach. The RS view gained less posterior exposure margin than the LS and EL views (posterosuperior margin values: RS, 4.3 ± 1.7 mm; LS, 6.4 ± 2.0 mm; EL, 7.3 ± 2.0 mm; P < 0.001; posteroinferior margin: RS, 2.7 ± 2.7 mm; LS, 4.9 ± 2.8 mm; EL, 8.3 ± 2.5 mm; P < 0.001). When the tentorium is intact, transverse sinus retraction significantly accentuates the field of view by the EL approach compared with the LS approach at both the anteroinferior (P < 0.05) and posteroinferior (P < 0.001) margins. Between the supracerebellar types, the vertical angle of attack was significantly improved and the horizontal angle was significantly decreased when complete venous retraction was performed.

Conclusion:

The supracerebellar views offer greater advantage over the RS view when the surgeon is working more posteriorly on the pontomesencephalic junction. Between the supracerebellar views, venous retraction creates a significantly wider vertical angle and also improves the exposure when the surgeon is working more inferiorly.

Lethal recurrent hemorrhages of a brainstem cavernoma

Hemorrhages of brainstem cavernomas may cause severe neurological deficits. Surgical strategies are frequently described, and advanced neuromonitoring with intraoperative imaging can help neurosurgeons to achieve good results. However, patients are often confronted with significant therapeutic risks by the primary doctor before talking to an experienced brainstem neurosurgeon. On the other hand, lethal progression with repeated hemorrhages is rarely described, although many would agree on this possibility by experience or assumption. Our reported case represents the natural development of a patient with repeated hemorrhages of a brainstem cavernoma and consequently increasing neurological deterioration, which led to a fatal ending. After two recurrent hemorrhages, the patient and his family declined twice the offered surgical procedures to evacuate the hematoma of the pons. The patient died after three noticed hemorrhages of the same brainstem cavernoma and their consecutive consequences. This case report represents one possible clinical scenario for consultation for brainstem cavernoma procedures.

Surgical treatment of symptomatic cavernous malformations of the brainstem

INTRODUCTION AND OBJECTIVES

Cavernous malformations (CM) at the level of the brainstem, continue to present a challenge in therapeutic terms and are an important source of controversy. Here we present our experience and the results obtained by adopting surgical treatment.

MATERIALS AND METHODS

The results of a consecutive series of 17 patients were studied. The surgical intervention was designed after: 1. A neurological examination. 2. MRI and cerebral angiography. 3. Correlation with anatomical brainstem maps. The surgical intervention was approached from the most damaged zone or through a zone which was functionally least important.

RESULTS

Complete extirpation was achieved in 15 patients without mortality. In a few patients the surgical intervention temporarily aggravated the prior lesion of the cranial nerves (2/17) or damage new sensory tracts (2/17). The functional post-operative recovery was good, in terms of consciousness (4/5), cranial nerves (11/17), the pyramidal tract (3/5) and the cerebellum (2/4). Of the patients that were operated, 14 of 17 returned to their professional activities.

CONCLUSIONS

The results of surgery can surpass the morbidity-mortality of the natural history or treatment with radiosurgery. There is a clear consensus in recommending surgical intervention for CMs that are superficially located, in young patients and in those with a risk of further bleeding. It is probably best that the surgery is performed during the subacute period, when the MRI offers a clear image confirming the presence of the CM.

Monitoring motor function during resection of tumours in the lower brain stem and fourth ventricle

OBJECTIVES

Even in the days of modern microsurgery, the removal of a brain stem lesion remains a surgical challenge. Especially when operating on children, the prognosis is directly related to the radicality of the resection; however, a radical resection is often associated with surgical morbidity. Intraoperative neuromonitoring could help to minimise the surgical morbidity, but few studies have been performed to clarify the value of this monitoring. We investigated a prospective series of 21 patients with lesions involving the brain stem for the prognostic value and benefits of neuromonitoring.

METHODS

We performed intraoperative neuromonitoring of cranial nerve function by electromyography (EMG) and motor evoked potential (MEP). The results were correlated with postoperative neurological deficits.

CONCLUSIONS

There is a good correlation between intraoperative neurophysiological events and postoperative neurological deficits in patients with lesions of the brain stem. In general, transient, prolonged, spontaneous activity in EMG is associated with a transient paresis of the respective muscle, whereas a permanent spontaneous activity is associated with a permanent deficit. Intraoperative neuromonitoring reliably predicts postoperative neurological function in patients with tumours of the lower brain stem and fourth ventricle. This neuromonitoring guides the neurosurgeon in the operation and may decrease surgical morbidity. We recommend using monitoring of MEP and EMG of the lower cranial nerves in surgery on all patients with lesions involving the lower brain stem and fourth ventricle.

Early surgery for brainstem cavernomas

BACKGROUND

The purpose was to review our experience with the surgical management of brainstem cavernomas (BSCs) and especially the impact of the surgical timing on the clinical outcome.

METHOD

We retrospectively reviewed 22 patients harboring a BSC, who underwent 23 procedures.

FINDINGS

Surgery was carried out during the early stage after the last haemorrhage, with a mean delay of 21.6 days (range 4-90 days). Sixteen procedures were performed after a first bleeding event while seven after multiple bleedings. Complete resection was achieved in 19 patients (86.4%). Early after surgery, 12 patients (52.2%) improved neurologically, 5 (21.7%) were stable and 6 (26.1%) worsened. New postoperative deficits were noted after 9 procedures (39.1%). Statistically significant factors for postoperative aggravation were: late surgery (P = 0.046) and multiple bleedings (P = 0.043). No patient operated on within the first 19 days after bleeding did worsen (n = 11), as opposed to 6 out of 12 who did when operated on later. After a mean follow-up of 44.9 months, 20 patients (90.9%) were improved, 1 patient (4.6%) was worse and 1 patient was lost to follow-up (4.6%), after reoperation for rebleeding of a previously completely resected cavernoma. Late morbidity was reduced to 8.6%. The mean Glasgow Outcome Scale (GOS) at the end of the follow-up period was 4.24, compared to a mean preoperative GOS of 3.22 (P<0.001). Complete neurological recovery of motor deficits, sensory disturbances, cranial nerves (CNs), internuclear ophtalmoplegia and cerebellar dysfunction were respectively 41.7%, 38.5%, 52.6%, 60.0% and 58.3%. Among the most affected CNs: CN 3, CN 5 and CN 7 were more prone to completely recover, respectively in 60.0%, 70.0% and 69.2%.

CONCLUSIONS

Surgical removal of BSCs is feasible in experienced hands with acceptable morbidity and good outcome. Early surgery and single bleeding were associated with better surgical results.

Pontine Cavernous Angioma Resected using the Subtemporal, Anterior Transpetrosal Approach Determined Using Three-dimensional Anisotropy Contrast Imaging: Technical Case Report

OBJECTIVE AND IMPORTANCE

We describe a case of brainstem cavernous angioma resected by the subtemporal, anterior transpetrosal approach, selected on the basis of three-dimensional anisotropy contrast (3-DAC) imaging.

CLINICAL PRESENTATION

A 64-year-old woman presented with sudden headache and gait disturbance. Anatomic magnetic resonance imaging showed a mass lesion in the left anterolateral part of the pons. On 3-DAC imaging, posteromedial compression of the left corticospinal and corticopontine tracts by the mass lesion was demonstrated.

INTERVENTION

The lesion was resected through the anterolateral side of the pons via the subtemporal, anterior transpetrosal approach. Neurological symptoms improved postoperatively, and postoperative 3-DAC imaging demonstrated preservation of the corticospinal and corticopontine tracts.

CONCLUSION

The technique of 3-DAC imaging may provide important information regarding neural tracts for the planning of brainstem surgery.

Tectal plate cavernoma—a special entity of brainstem cavernomas

BACKGROUND

Brainstem cavernous malformations (BCM) have a high incidence of bleeding and rebleeding and carry a high rate of neurologic morbility. Locations in the tectal plate that represent a small percentage of BCMs have rarely been reported in the literature. The authors present a case of a patient with such localization who was successfully operated.

CASE DESCRIPTION

A 24-year-old male known for having a tectal plate cavernoma with obstructive hydrocephalus, previously treated by shunting in another hospital, was admitted in our institute because of increasing headaches, gradual drowsiness, and the inability to stand up. Investigations revealed a compressive cavernoma lateralized on the left side of the tectal plate and a residual hydrocephalus in spite of the previous shunting. A new shunting procedure did not improve clinical conditions. Thus, an aggressive surgical resection was decided upon and was performed through an occipital-transtentorial approach with the aid of intraoperative brainstem and middle latency auditory evoked potentials (BAEPs/MLAEPs) monitoring. Total resection was achieved without significant deterioration except a hypovoltage of wave V after stimulation of the right ear, demonstrating a left collicular dysfunction. The patient was discharged on the 36th day after surgery. Seven months later, audiometry was normal, in spite of the persistence of the hypovoltage of the V wave after stimulation of the right ear, and functional status appraised using the Karnofsky score was at 100%. Professional activity could be resumed.

CONCLUSION

Tectal plate cavernomas (TPC) represent a special entity of BCM. They are surgically accessible lesions on the dorsal aspect of the brainstem. Our preferred approach is the occipital-transtentorial approach. The use of intraoperative auditory evoked potentials monitoring make the surgical resection safer.

Surgical management of brain-stem cavernous malformations: report of 137 cases

BACKGROUND

With the improvement in neuroimaging and microsurgical techniques, brain stem cavernous malformations are no longer considered inoperable. Surgical indications for brainstem cavernoma are evolving, with better understanding of its natural history and decreasing surgical complications.

METHODS

During 1986 through 1998, a series of 137 patients (4 patients each with two brain stem lesions, total number of lesions, 141) with brain stem cavernous malformations were treated microsurgically at Beijing Neurosurgery Institute. The age distribution, lesion location, and clinical presentations were analyzed. The bleeding rate, surgical indications and microsurgical techniques were also discussed.

RESULTS

In our series, 92 of 137 cases (67.2%) suffered more than one hemorrhage. Female patients had a higher risk of recurrent hemorrhage than that of male patients. Unlike cavernomas malformations from other locations, repeated hemorrhages from brain stem malformations are much more common and usually lead to new neurologic deficits. Among all 137 surgically treated patients, there was no operative mortality. Ninety-nine patients (72.3%) either improved or remained clinically stable postoperatively. The size of the cavernoma/hematoma does not necessarily correlate with the surgical result. While the acute hematoma can facilitate the surgical dissection, longer clinical history with multiple hemorrhages often makes total surgical resection difficult, partially because of the firmer capsule that may not shrink or collapse after hematoma is released. Pathologically those capsules were associated with more hyaline degeneration, fibrous proliferation and even calcifications. During the follow-up period between 0.5 to 11 years in 129 cases, 115 patients (89.2%) have been working, studying, or doing house work. Three patients (2.3%) suffered recurrent hemorrhages.

CONCLUSIONS

Surgical indications of brain stem cavernoma include (1) progressive neurologic deficits; (2) overt acute or subacute hemorrhage on MRI either inside or outside cavernous malformations with mass effect; (3) cavernoma/hematoma reaching brainstem surface (<2 mm brain tissue between cavernoma /hematoma and pial surface). Grave clinical presentations like coma, respiratory, or cardiac instability are not surgical contraindications. Emergent surgical evacuation may lead to satisfactory outcome. Repeated hemorrhages will worsen the pre-existing neurologic deficits and possibly make the surgical dissections more difficult. Patients with minimum, stable neurologic deficits and lesion/hematoma that has not reached the brain stem surface should be followed conservatively.

Preoperative Evaluation of Neural Tracts by Use of Three-dimensional Anisotropy Contrast Imaging in a Patient with Brainstem Cavernous Angioma: Technical Case Report

OBJECTIVE AND IMPORTANCE

We describe a case of brainstem cavernous angioma in which the neural tracts were evaluated before surgery by three-dimensional anisotropy contrast (3-DAC) magnetic resonance imaging.

CLINICAL PRESENTATION

A 64-year-old man presented with a cavernous angioma located intrinsically in the brainstem and manifesting as gait ataxia. 3-DAC imaging demonstrated that the lesion was located outside the left inferior cerebellar peduncle and inside the middle cerebellar peduncle.

INTERVENTION

The intact brain surface was incised, and the lesion was removed successfully on the basis of the preoperative 3-DAC images. The patient exhibited temporary exacerbation of his gait ataxia, but the symptom improved 3 months after surgery. Postoperative 3-DAC imaging demonstrated resection of the lesion and preservation of the left inferior and middle cerebellar peduncles.

CONCLUSION

3-DAC imaging may provide essential information about the neural tracts for the planning of brainstem surgery.

Transposition of the oculomotor nerve for resection of a midbrain cavernoma. Technical note

The authors discuss the utility of anterior transposition of the oculomotor nerve from the lateral wall of the cavernous sinus to widen the corridor posterior to the cisternal segment of the oculomotor nerve; this allows exposure of the anterolateral surface of the midbrain. This additional exposure was successfully used for the resection of a large calcified cavernoma in the upper brainstem of a 67-year-old woman who had presented with sudden onset of left hemiparesis and oculomotor palsy. The patient's postoperative course was uneventful and she displayed symptomatic improvement.

Surgical management of brainstem cavernomas

OBJECT

A careful retrospective analysis of 36 cases was performed to evaluate the pre- and postoperative rates of morbidity that occur in patients with brainstem cavernous angiomas.

METHODS

The authors evaluated immediate postoperative and follow-up outcomes with regard to clinical findings, the incidence of preoperative hemorrhage(s), location and size of the lesions, and the timing of the surgical procedure after the last hemorrhagic event. Specifically. the following parameters were analyzed: 1) number of hemorrhages; 2) the precise brainstem location (pontomesencephalic, pons, and medulla oblongata); 3) pre- and postoperative cranial nerve status; 4) pre- and postoperative motor and sensory deficits; 5) size (volume) of the lesions; and 6) pre- and postoperative Karnofsky Performance Scale (KPS) scores. Multiple hemorrhages were observed in 16 patients, particularly in those with pontomesencephalic cavernous angiomas (75%). The mean preoperative KPS score was 70.3 +/- 16.3 (+/- standard deviation). Twenty-six patients (72.2%) presented with cranial nerve impairment, 13 (36.1%) with motor deficits, and 17 (47.2%) with sensory disturbance. Volume of the lesions ranged from 0.18 to 18.18 cm3 (mean 4.75 cm3). Postoperative complications included new cranial nerve deficits in 17 patients, motor deficits in three, and new sensory disturbances in 12 patients. In a mean follow-up period of 21.5 months, KPS scores were 80 to 100 in 22 patients. Timing of surgery (posthemorrhage) and multiple hemorrhages did not influence the long-term results. Higher preoperative KPS scores and smaller-volume lesions, however, were factors associated with a better final outcome (p < 0.05). Major morbidity was related mainly to preoperative status and less to surgical treatment. The incidence of new postoperative cranial nerve deficits was clearly lower than that demonstrated preoperatively because of the brainstem hemorrhages.

CONCLUSIONS

Based on these findings, resection of brainstem cavernomas is the treatment of choice in the majority of these cases because of the high incidence of morbidity related to one or often several brainstem hemorrhages.

Transoral transclival removal of anteriorly placed cavernous malformations of the brainstem

BACKGROUND

The natural history of brain stem cavernous malformations is unfavorable because of their high hemorrhage rate and resulting neurological deterioration among patients. However, direct surgery of intrinsic and anteriorly situated cavernomas is hazardous and leads to a bad postoperative outcome because of trauma to lateral and dorsally situated eloquent areas of the brain stem.

METHODS

We review the cases of two patients with symptomatic cavernous malformations of the anterior brain stem and describe the usefulness of a transoral-transclival approach. A 23-year-old man developed progressive hemihypaesthesia and paraesthesia, hemiparesis with gait ataxia, dysarthria, dysphonia, and dysphagia. A 38-year-old woman suffered from an acute onset of vertigo with nausea and vomiting, diplopia, and paraesthesia of the left hand and foot. In both patients, computed tomography demonstrated the presence of brain stem hemorrhage, because of cavernous malformation. Magnetic resonance imaging showed a close proximity of the lesions to the pia mater only on the ventral surface of the brain stem.

RESULTS

In both patients, the cavernomas could be safely approached and completely resected via a transoral transclival route. Three months after surgery, neurological examination revealed marked neurological improvement. The 23-year-old patient showed slight gait ataxia, no hemiparesis, no cranial nerve palsies; the 38-year-old woman demonstrated no neurological symptoms except for minimal motor dysfunction of the left hand. In both cases, under perioperative prophylactic antibiotics, no meningitis was observed. The patients could subsequently return to their previous employment.

CONCLUSION

The transoral transclival approach for ventrally situated brain stem cavernomas allows a largely atraumatic resection of the lesion.

Persistent hiccup as presenting symptom in medulla oblongata cavernoma: a case report and review of the literature

A rare case of persistent intractable hiccup as presenting symptom of cavernous angioma in the medulla oblongata is reported. Pathophysiologic hypotheses about the triggering mechanism of hiccup are discussed, with special reference to the causes affecting the central nervous system. A review of the literature concerning medullary lesions presenting with persistent hiccup is also reported. Finally we have included some brief considerations about cavernous angiomas and the patterns of their clinical presentation, focusing on those located in the medulla oblongata.

Intraoperative electrical stimulation for identification of cranial nerve nuclei

The purpose of this study was to evaluate the feasibility and usefulness of cranial nerve nuclei monitoring during resection of brainstem cavernous malformations. Eleven patients with brainstem cavernous malformations underwent resection of their malformations utilizing cranial nerve nuclei monitoring. Cranial nerves V and VII were monitored by placing electrodes in muscle groups innervated by these nerves and recording manipulation-induced neurotonic discharges and triggered electromyographic (EMG) activity, after electrical stimulation of the corresponding brainstem nuclei. Seven of 11 procedures (64%) with cranial nerve nuclei monitoring were noted to have cranial nerve nuclei activity corresponding to manipulation of the nuclei. The cavernous malformation was completely resected in 5 of 7 cases with cranial nerve nuclei activity and in all 4 cases without activity. In the remaining 2 cases, the cavernous malformation was not resected due to the proximity of the monitored cranial nerve nuclei to the cavernous malformation and to increasing neurotonic activity as the cavernous malformation was approached. None of the 11 patients had new permanent postoperative deficits corresponding to the cranial nerve nuclei monitored; 1 patient had a transient partial facial palsy lasting 2 days. Preliminary results indicate that cranial nerve nuclei monitoring proves useful in preserving neurologic function and reducing surgical morbidity during resection of brainstem cavernous malformations, particularly indicating when lesion resection places these nuclei at risk.

Cavernous angiomas of the brain stem. Intra-axial anatomical pitfalls and surgical strategies

BACKGROUND

We review the surgical anatomy of the brain stem in relation to the surgical approaches adopted for treatment of cavernomas and identify possible "safe entry zones" on the anterior face of the brainstem.

METHODS

Twelve symptomatic patients with cavernoma or telangectasia of the brain stem were surgically treated. The brain stem was divided into the following anatomical areas: ventral medulla, dorsal medulla, dorsal pons, ventral pons, ventral mesencephalon, and dorsal mesencephalon, so that the surgical approach could be "individualized" according to the position of the cavernoma, the nerve fasciculi and nuclei.

RESULTS

On the anterior surface of the brain stem a medullar paramedian oblique access to the anterolateral sulcus and a paramedian sagittal pons access seem to avoid the main nerve fasciculi and nuclei.

CONCLUSIONS

Although the parenchymal window produced by the cavernoma is the most important parameter for the choice of approach, fairly safe entry zones may be identified even on the anterior surface of the medulla and pons.

Transcollicular approach to intrinsic tectal lesions

OBJECTIVE

We used a paramedian, infratentorial-supracerebellar, transcollicular approach to resect 11 intrinsic tectal lesions, including 8 tumors and 3 hematomas, in 11 patients. The route of access to the lesions was designed to minimize the anatomic and functional damage to the surrounding structures.

METHODS

Access was through one superior colliculus in each of seven patients, through one inferior colliculus in each of two patients, and through the superior and inferior colliculi of one side in each of two patients.

RESULTS

Of the eight tumors, three were totally resected, four were nearly totally resected, and one was partially resected. The preoperative ocular symptoms did not change in six of these eight patients and worsened in two, and the neurological deficits, except ocular symptoms, improved in two. All three hematomas were completely removed, along with abnormal blood vessels in the wall of the hematoma cavity; all three of these patients experienced neurological improvement.

CONCLUSION

We conclude that the paramedian, infratentorial-supracerebellar, transcollicular approach permits safe removal of intrinsic tectal lesions. Resection of the superior or inferior colliculus or both on one side seems to be neurologically well tolerated.

Middle fossa transpetrosal approach for petroclival and brainstem tumors

OBJECTIVE

The purpose of the study was to demonstrate the utility of the middle fossa transpetrosal approach with anterior petrosectomy for difficult-to-access petroclival and pontine lesions.

STUDY DESIGN

Retrospective case review in academic tertiary referral center.

METHODS

Patients for inclusion had pontine and prepontine lesions of the petroclival region. Middle fossa transpetrosal approach with anterior petrosectomy with excision or biopsy of the lesion was performed. The main outcome measure was postoperative neurologic status including motor and cranial nerve function.

RESULTS

No patient experienced neuromuscular compromise or cranial nerve deficits as a direct result of the surgical procedure. Complications consisted of a subdural temporal lobe hemorrhage and one case of cerebrospinal fluid rhinorrhea.

CONCLUSIONS

The middle fossa transpetrosal approach with anterior petrosectomy was utilized for five patients with petroclival or pontine tumors. In this small series, it served well to spare cranial nerves and allowed avoidance of serious vascular injury. To our knowledge, this is the first reported use of this procedure for pontine venous angiomas.

Cavernous angioma presenting with hemidystonia

We present a 34-year-old woman with right hemidystonia. She had a cavernous angioma (CA) of left thalamo-mesencephalic junction, revealed by magnetic resonance imaging (MRI). Her symptoms were moderately alleviated by biperiden 20 mg daily. We identified 11 patients reported in the literature to have movement disorders due to a cavernous angioma. None of them presented with hemidystonia. Some clinical properties of patients with CA associated with a movement disorder were evaluated.

Pathological changes in surgically resected angiographically occult vascular malformations after radiation

OBJECTIVE

The goal of this study was to evaluate the pathological changes associated with radiation treatment (stereotactic radiosurgery or conventional irradiation) of angiographically occult vascular malformations (AOVMs).

METHODS

Eleven patients underwent surgical resection of an AOVM in the mesial temporal lobe, brain stem, thalamus, or basal ganglia after previous radiation treatment. The indications for surgery were recurrent symptomatic bleeding from the lesion in 10 patients and recurrent intractable seizures in 1 patient. Radiation was used as the initial therapy because the risk of surgical resection was deemed too high. Three patients received conventional radiation therapy of 3000 to 5400 rads at an outside institution. One patient received radiosurgery with the gamma knife at another institution using a dose of 15 Gy to the margin. The remaining 7 patients received stereotactic radiosurgery with a helium-ion particle beam. The dose range was from 18 to 26 Gy equivalents. The interval from radiation to surgical resection ranged from 1 to 10 years, with a mean of 3.5 years. These lesions were compared with 10 nonirradiated cavernous malformations.

RESULTS

One irradiated lesion was identified pathologically as a true arteriovenous malformation despite being angiographically occult. This lesion did not demonstrate significant changes in the vasculature but did have radiation necrosis of the surrounding brain 5 years after 25 Gy equivalents of helium-ion radiosurgery. Two other specimens were too small to identify the type of vascular malformation adequately. Of the remaining eight malformations identified as cavernous malformations, six showed a combination of marked fibrosis of the vascular channels, fibrinoid necrosis, and ferrugination. However, the fibrinoid necrosis was the only finding unique to the irradiated lesions compared with nonirradiated controls. All the irradiated lesions still had patent vascular channels; none were completely thrombosed.

CONCLUSION

Radiosurgery or conventional radiation therapy did not cause histologic vascular obliteration in intracranial AOVMs evaluated 1 to 10 years (mean 3.5 yr) after radiation delivery. It should be recognized that these patients are irradiation failures who may not be representative of all irradiated patients. However, recurrent bleeding from AOVMs may relate to poor radiation response in some patients.

The anatomical aspects of a surgical approach through the floor of the fourth ventricle

In 1993 Kyoshima et al. introduced safe entry zones in the region of the 4th ventricle floor: infrafacial triangle and suprafacial triangle. Is it possible to demarcate these zones precisely in every case intra-operatively? A postmortem study of 40 brainstems of patients who had died of non-brain disease was performed to evaluate the degree of individual morphological and morphometrical variability of the 4th ventricle floor. The purpose of this study was to find constant landmarks and distances within the rhomboid fossa region which would help a neurosurgeon to determine safe approach zones through the 4th ventricle floor to brainstem lesions. Several anatomical landmarks-median sulcus, obex, vestibular area, vagal triangle, hypoglossal triangle-were found to be sufficiently visible in all examined brainstems. However, the facial colliculus which is a border structure between the infrafacial and suprafacial safe approach zone was poorly visible in about 37% of the analyzed material. The striae medullares were not found to be good orientation structures as they were not visible in 30% of the material and exhibited individual variability of a high degree in relation to their number and arrangement. In the morphometrical study analyzed measurements were taken by utilizing the digital image analyzer MULTISCAN. Based on the results obtained the authors suggest new borders of the infrafacial safe approach zone and morphometrical directions to determine the suprafacial safe approach zone in cases when the facial colliculus is not clearly visible or invisible intra-operatively.

Early radiologically proven rebleeding from intracranial cavernous angiomas: report of 6 cases and review of the literature

Although intracranial cavernomas are known to cause haemorrhage, data concerning the frequency, severity and delay of recurrent bleedings are controversial. We report a series of 6 patients with histologically proven cavernoma, presenting with early clinical signs and radiological proof of rebleeding, that is occurring in the first month after initial overt haemorrhage. These 6 cases have been selected from a series of 142 patients seen between 1980 and 1995 in our department with cavernous angiomas or so-called AOVMs, of whom 93 presented with clinical symptoms of haemorrhage (34 patients presented symptoms of one or more rebleeding, but only 6 had radiological proof). All patients suffered neurological worsening due to the rebleeding, with an increase of the size of the haematoma on the CT scan. Five MRIs were performed at the acute stage: 3 showed evidence of cavernoma (60%). All patients underwent surgery at the acute stage of the rebleeding, with 5 improvements and 1 stabilization. A cavernous angioma was found in 5 cases at first surgery, but a further operation was necessary in the last patient to find and remove the cavernoma, after a second rebleeding following the first intervention. Our series reveals a high frequency of rebleeding after a first intracranial haemorrhage from a cavernous angioma, and highlights the precocity of such rebleedings. Therefore, we advocate early aggressive surgical management: in cases of cavernoma revealed by a first clinical overt haemorrhage, when there is strong radiological suspicion at the acute stage; and in all cases of rebleeding, even without radiological evidence of malformation, in the absence of vascular risk factors. Surgical indication must be discussed in particular cases of cavernomas of the brain stem when neither the haematoma nor the cavernoma reach the surface, and in deep supratentorial cavernomas, when the neurological status is good, because of the therapeutic risk.

Experimental study for identification of the facial colliculus using electromyography and antidromic evoked potentials

OBJECTIVE

The facial colliculus is a reliable landmark for a surgical approach via the fourth ventricle. Our aim is to elucidate the most suitable electrophysiological methods for identification of the facial colliculus. We evaluated the usefulness of facial electromyography and antidromic evoked potentials of the facial nerve. The effect of stimulation on cardiorespiratory function is also studied.

METHODS

We localized the facial colliculus by facial electromyography and antidromic facial evoked potentials in adult dogs. To determine the most effective stimulus pattern, intensity was varied, and both monopolar and bipolar electrical stimulation were tried. To confirm the cardiorespiratory effect of the stimulation, systemic blood pressure, heart rate, respiratory rate, and thoracic excursion were measured. After administration of atropine sulfate, changes in vital signs were recorded.

RESULTS

A stable facial electromyographic wave form was produced by 0.1-mA monopolar stimulation of a small portion of the fourth ventricular floor (4 mm2). Using 0.1-mA bipolar stimulation, the same wave form was obtained. As saline was gradually added around the electrodes, the amplitude of the response gradually decreased; however, the response with monopolar stimulation was more stable than that with bipolar stimulation. Stimulation of the facial colliculus with greater than 2 mA caused transient hypotension and bradycardia; respiratory arrest occurred with 3 mA stimulation. Administration of atropine sulfate (0.01 mg/kg) decreased these responses. Antidromic facial evoked potentials were recorded only at "hot points" that existed within 2 mm of the facial colliculus.

CONCLUSION

Our study resulted in three findings. First, the most suitable electrophysiological stimulation of the fourth ventricular floor for identification of the facial colliculus was 0.1-mA monopolar stimulation. Second, significant alteration in cardiorespiratory function appeared with greater than 1-mA stimulation. Third, a recording of an antidromic facial evoked potential can identify the facial colliculus more safely than direct stimulation of the facial colliculus. Both orthodromic and antidromic methods were useful for identification of the facial colliculus in brain stem surgery.

Surgical management of brain-stem cavernomas

We present a series of seven patients who were operated on for symptomatic brain-stem cavernomas. The following approaches were used: medial suboccipital (N = 4), lateral suboccipital (N = 1), subtemporal-transtentorial (N = 1), and frontal transcortical-transventricular-subchorioidal-trans velum interpositum (N = 1). Intraoperative motor (N = 4) and somatosensory (N = 1) evoked potential monitoring revealed temporary changes in 3 patients. Immediately postoperatively, the following additional deficits were observed in 6 patients: oculomotor nerve paresis (N = 2), abducens nerve paresis (N = 3), facial nerve paresis (N = 2), deafness (N = 1), and increased ataxia (N = 3). One patient died due to septic complications not related to surgery. After a mean observation time of 2 years, 2 patients had improved, 3 were unchanged, and 1 patient deteriorated as compared to his preoperative status. In conclusion, surgical treatment of brain-stem cavernomas, although carrying a significant risk of temporary neurological deterioration is recommended in symptomatic patients in whom the cavernoma seems to reach the surface of the brain-stem. Intraoperative functional topographic mapping and monitoring have proven useful tools lowering the surgical risks in these patients.

Successful removal of cryptic arteriovenous malformation located at the upper ventral pons via subtemporal transtentorial approach

BACKGROUND

Lesions located at the ventral portion of the brain stem are still difficult to access surgically. We report herein a case of ventral pontine cryptic arteriovenous malformation that was successfully removed via a subtemporal-transtentorial approach.

CASE REPORT

An 18-year-old female patient experienced repetitive hemorrhagic attacks leading to a massive pontine hemorrhage with several neurologic deficits. Since angiography and magnetic resonance imaging failed to delineate the hemorrhagic origin, a combination of multiple approaches was initially attempted. The subtemporal-transtentorial approach made it possible to obtain an adequate operative view in this case. An angioma observed at the septum of the multilocular hematoma was totally removed. Pathologic examination of the resected specimen revealed it to be an arteriovenous malformation. Postoperatively, the patient showed unexpectedly good recovery despite the original massive pontine hemorrhage.

CONCLUSIONS

Several surgical approaches to the ventral pons have been proposed in the literature. While the subtemporal-transtentorial approach was useful in our patient, multiple routes should be considered to access a massive lesion of unknown extent at the ventral pons. The unexpected recovery observed in our patient suggests that surgery is an option in the treatment of this type of lesion.

Intra-axial endophytic primitive neuroectodermal tumors in the pons: clinical, radiological, and immunohistochemical aspects in four children

We present the clinical findings, radiological aspects, operative results, and histopathological features of four typical primitive neuroectodermal tumors (PNET) located in the pontine region in children. All the tumors had an endophytic intra-axial growth pattern. All the children had a short history of severe neurological deficits with involvement of the cranial nerves and pyramidal tract. MRI did not reveal any common feature of malignancy. Compared to our successful experience in operations of intra-axial endophytic brainstem tumors in a total of 32 children, the outcome was poor: all 4 children died within 13 months. We conclude that PNET occurring in the pons is not as rare as was believed, and, compared to PNET in other areas the prognosis is worse.