Experimental study of medullary trigeminal evoked potentials: development of a new method of intraoperative monitoring of the medulla oblongata

Stereotactic LINAC radiosurgery for the treatment of typical intracranial meningiomas. Efficacy and safety after a follow-up of over 12 years

PURPOSE

The efficacy and safety of stereotactic radiosurgery (SRS) for treatment of intracranial meningiomas has been demonstrated in numerous studies with short- and intermediate-term follow-up. In this retrospective single-center study, we present long-term outcomes of SRS performed with a linear accelerator (LINAC) for typical intracranial meningiomas.

PATIENTS AND METHODS

Between August 1990 and December 2007, 148 patients with 168 typical intracranial meningiomas were treated with stereotactic LINAC-SRS, either as primary treatment or after microsurgical resection. A median tumor surface dose of 12 Gy (range 7-20 Gy) and a median maximum dose of 24.1 Gy (range 11.3-58.6 Gy) was applied. The median target volume was 4.7 ml (range 0.2-32.8 ml, SD ± 4.8 ml).

RESULTS

Overall mean radiological follow-up was 12.6 years. Tumor shrinkage was seen in 75 (44.6 %) and stable disease in 85 (50.6 %) cases. Eight of 168 meningiomas (4.8 %) showed local tumor progression. The tumor control rate (TCR) after 5, 10, and 15 years was 93.6 % at each time point, and the progression-free survival (PSF) rates were 92, 89, and 89 %, respectively. The neurological symptoms existing prior to LINAC-SRS improved in 77 patients (59.7 %), remained unchanged in 42 (32.6 %), and deteriorated in 10 (7.8 %) patients.

CONCLUSION

Our study emphasizes the efficacy of LINAC-SRS for de novo, residual and recurrent typical intracranial meningiomas. A high long-term local TCR with a low morbidity rate could be achieved. LINAC-SRS should thus be considered as a primary treatment option, as one arm of a combined treatment approach for incompletely resected meningiomas, or as a salvage therapy for recurrences.

Management of spheno-orbital en plaque meningiomas: clinical outcome in a consecutive series of 40 patients

OBJECTIVE

The clinical results of combined surgical-radiosurgical treatment of the spheno-orbital en plaque meningiomas in a consecutive series of 40 patients are presented. The clinical outcome is evaluated in terms of surgical morbidity, tumour control, visual function and cosmetic result.

METHODS

Forty patients harbouring spheno-orbital en plaque meningiomas were treated. Forty-two surgical procedures were performed through a fronto-temporal craniotomy. The reconstruction of the orbital walls was performed using a titanium mesh. In case of sub-total resection, the patients underwent Gamma-Knife radiosurgery on residual tumour. Visual function was evaluated considering visual acuity tested with a Snellen chart, funduscopy and Goldmann perimetry for visual field defects. Proptosis was quantified on CT scans.

RESULTS

Total or gross-total tumour resection was achieved in 56.1% of cases. Permanent morbidity was recorded in three patients after surgery. Visual acuity and visual field defect both improved in 66.7% of patients; improvement of proptosis was recorded in 92.7% of cases. Eighteen patients were treated with Gamma-Knife radiosurgery for residual tumour after surgery and four patients for tumour relapse at follow-up. The mean follow-up period was 72.6 months.

CONCLUSIONS

Surgical treatment of spheno-orbital en plaque meningiomas is safe and effective: a low morbidity rate was recorded and visual function improved in about two-thirds of patients. Reconstruction of the orbital walls with titanium mesh provides for good functional and cosmetic results. In case of superior orbital fissure and cavernous sinus invasion, the combined surgical-radiosurgical treatment allows to minimise surgical morbidity and to achieve tumour control.

The human locus coeruleus 3-D stereotactic anatomy

PURPOSE

The main goal of this work was to study the stereotactic anatomy of the human locus coeruleus (LC), important relay of adrenergic and dopaminergic human brainstem (HB) circuitry, to allow its easy localization on MRI and in microsurgical procedures.

METHODS

Forty LC were studied from 20 adult HB of both sexes. The melanin pigmentation of its cells was used to identify and localize them and so to define the 2-D and 3-D LC contours. These HB were cut on a cryomicrotome with 3-D referenciation. The slices were coloured with haematoxyline-eosin. On the slices, digitized images of the cells were referenced to the midline, the fourth ventricle floor plane and the pontomedullary junction plane with an appropriate computer program.

RESULTS

The LC revealed to be a symmetric, thin and elongated nucleus, divergent caudally except in its superior part, with a sub-ependymal location on the superior dorsal lateral pons. The main LC dimensions are: length 12.0-17.0 mm (m 14.5); width 2.5 mm; height 2.0 mm. The 3-D references of the LC center are: 3.2 ± 0.3 mm to the midline; 1.1 ± 0.2 mm to the IV ventricle floor and 18.5 ± 1.5 mm to the ponto-medullary junction.

CONCLUSIONS

The human LC is a nucleus thinner and longer than previously described (in average 14.5 mm long and 2-2.5 mm thick), localized 1 mm under the IV ventricle, 3 mm apart from the midline and centered 14-21 mm above de ponto-medullary junction. No correlation was found between LC and pons dimensions, the gender or the age.

Blood flow disturbance in perforating arteries attributable to aneurysm surgery

Object

The object of this study was to investigate patients with cerebral infarction in the area of the perforating arteries after aneurysm surgery.

Methods

The authors studied the incidence of cerebral infarction in 1043 patients using computed tomography or magnetic resonance imaging and the affected perforating arteries, clinical symptoms, prognosis, and operative maneuvers resulting in blood flow disturbance.

Results

Among 46 patients (4.4%) with infarction, the affected perforating arteries were the anterior choroidal artery (AChA) in nine patients, lenticulostriate artery (LSA) in nine patients, hypothalamic artery in two patients, posterior thalamoperforating artery in five patients, perforating artery of the vertebral artery (VA) in three patients, anterior thalamoperforating artery in nine patients, and recurrent artery of Heubner in nine patients. Sequelae persisted in 21 (45.7%) of the 46 patients; 13 (28.3%) had transient symptoms and 12 (26.1%) were asymptomatic. Sequelae developed in all patients with infarctions in perforating arteries in the area of the AChA, hypothalamic artery, or perforating artery of the VA; in four of five patients with posterior thalamoperforating artery involvement; and in two of nine with LSA involvement. The symptoms of anterior thalamoperforating artery infarction or recurrent artery of Heubner infarction were mild and/or transient. The operative maneuvers leading to blood flow disturbance in perforating arteries were aneurysmal neck clipping in 21 patients, temporary occlusion of the parent artery in nine patients, direct injury in seven patients, retraction in five patients, and trapping of the parent artery in four patients.

Conclusions

The patency of the perforating artery cannot be determined by intraoperative microscopic inspection. Intraoperative motor evoked potential monitoring contributed to the detection of blood flow disturbance in the territory of the AChA and LSA.

Linear accelerator surgery for meningiomas

Object. In this paper the authors review the results of a single-center experience in the use of linear accelerator (LINAC) surgery for radiosurgical treatment of meningiomas.

Methods. A retrospective analysis of all patients treated with LINAC surgery for meningiomas between May 1989 and December 2001 was performed. All patients participated in follow-up review for a minimum of 2 years, and no patients were excluded. Two hundred ten patients were treated during the study interval.

The actuarial local control rate for benign tumors was 100% at both 1 and 2 years, and 96% at 5 years. The actuarial local control rate for atypical tumors was 100% at 1 year, 92% at 2 years, and 77% at 5 years; and that for malignant tumors was 100% at both 1 and 2 years, and only 19% at 5 years. Of the 210 patients 13 (6.2%) experienced temporary radiation-induced complications, and only five (2.3%) experienced permanent complications. In all patients with a permanent complication the histological characteristics of the meningioma were malignant.

Conclusions. Linear accelerator surgery produced high local control rates and very low rates of permanent morbidity in patients harboring benign meningiomas.

Gamma knife surgery for epilepsy related to hypothalamic hamartomas

OBJECTIVE

Drug resistant epilepsy associated with hypothalamic hamartoma (HH) can be cured by microsurgical resection of the lesion. Morbidity and mortality risks of microsurgery in this area are significant. Gamma Knife Surgery's (GKS) reduced invasivity seems to be well adapted. In view of the severity of the disease and risks of surgical resection it is crucial to evaluate GKS for this indication. A first retrospective study has shown a very good safety and efficacy level but for a more reliable evaluation a prospective study would be required.

METHODS

Between Oct 1999 and July 2002, 30 patients with HH and associated severe epilepsy were included. Seizure semiology (video EEG) and frequency, behavioural disturbances, neuropsychological performance, endocrinological status, sleep electroclinical abnormalities, MR imaging, and visual function were systematically evaluated before and after GKS (6, 12, 18, 24, 36 months). Twenty patients had experienced precocious puberty at a median age of 3,7 (0-9). Range of maximum diameter was from 7,5 to 23 mm with only 3 larger than 18 mm. The median marginal dose was 17 gy (14-20).

RESULTS

Sufficient follow up for final evaluation is not yet available. Only 6 patients have a follow-up of more than 12 months and 19 more than 6 months. However a lot of very dramatic changes did occur during that period in this group. Among the 19 patients with more than 6 months of follow-up, a lot had already experienced an increase of gelastic seizures around 3 months (3), an improvement in their seizure rate (18), behaviour (9), sleep (3), and EEG background activity (3), a cessation of partial complex seizures (7). No complications have occurred till now except one patient experiencing at 5 months a hyperthermia without infection and concomitant increase of gelastic seizures both ceasing suddenly and spontaneously after 15 days.

CONCLUSION

Our first results indicate that GKS is as effective as microsurgical resection and very much safer. GKS also allows to avoid the vascular risk related to radiofrequency lesioning or stimulation. The disadvantage of radiosurgery is its delayed action. Longer follow-up is mandatory for a serious evaluation of the role of GKS. Results are faster and more complete in patients with smaller lesions inside the 3rd ventricle (grade II). The early effect on subclinical discharges turns out to play a major role in the dramatic improvement of sleep quality, behaviour, developmental acceleration at school.

Cyst formation following gamma knife surgery for intracranial meningioma

Object.The authors conducted a study to evaluate the clinical significance of cyst formation or enlargement after gamma knife surgery (GKS) for intracranial benign meningiomas.

Methods.The medical records of 160 patients with 184 tumors were examined for those with follow-up data of more than 2 years among 270 patients who underwent GKS for intracranial meningiomas between February 1992 and November 2001.

Cyst formation or enlargement following GKS was observed in five patients, one man and four women (mean age 61.2 years). The tumor location was the sphenoid ridge in one case, petroclival in two, tentorium in one, and parasagittal region in one. All patients underwent surgery before GKS. The mean tumor volume was 10.5 cm3, the mean margin dose was 13.4 Gy (median 14 Gy), and the mean maximum dose was 27.5 Gy (median 24.1 Gy). At the time of GKS three tumors were associated with cyst, of which two enlarged after radiosurgery. Three cysts developed de novo after GKS. Three of the five patients needed surgery to treat the cyst formation or enlargement. Histological examination demonstrated various findings such as tumor necrosis, proliferation of small vessels, vascular obliteration, and hemosiderin deposits.

Conclusions.New cyst formation following GKS for benign intracranial meningioma is relatively rare; however, both preexisting and newly developed cysts tend to enlarge after GKS and often require surgery.

Volume reduction in meningiomas after gamma knife surgery

Object.The purpose of this study was to evaluate the volume-reducing effects of gamma knife surgery (GKS) of meningiomas with and without previous surgical treatment.

Methods.A group of 127 patients with a mean age of 57.1 years (range 9–81 years) with 142 meningiomas (128 World Health Organization Grade I and 14 Grade II) were included in this study. The management strategy reduces tumor volume with surgery when necessary (81 patients). Stereotactic GKS with a Gamma Knife model C was performed in all tumors of suitable size. Magnetic resonance imaging follow-up examinations with volumetric tumor analysis was performed 6 months after treatment and annually thereafter.

The mean tumor volume was 5.9 cm3(range < 5 to > 40 cm3). The mean follow-up time after GKS was 29.3 months (range 11–61 months). The mean prescription dose was 13.8 Gy (range 10–18 Gy). A reduction in volume occurred in 117 (82.4%) of all tumors, and in 20 tumors (14.1%) growth ceased. The overall tumor control rate of 96.4%. The mean volume reduction achieved with GKS was more than 46.1%. Only five tumors (3.5%) showed a volume increase.

Conclusions.Gamma knife surgery was effective in reducing meningioma volume at short-term follow up. Further studies are needed to examine the development of these findings over a longer period.

Gamma Knife Radiosurgery of Skull Base Meningiomas

Meningiomas are the most frequent benign tumors treated by gamma knife radiosurgery and the majority of them are located on the skull base. Between 1992 and 1999, 197 skull base-located meningiomas in 192 patients were treated by gamma knife in Prague. Contact with the chiasma or optic tract was not regarded as a contraindication for gamma knife radiosurgery and such contact was observed in 32% of the skull base meningiomas treated. 176 patients were monitored during a median of 36 months, of whom 73% showed a decrease in tumor volume; no change was observed in 25% and continued growth was observed in 2%. Neurodeficit improved in 63% of patients, temporary morbidity occurred in 11% and persistent morbidity remained in 4.5%. Radiosurgery induced edema in 11%. Significantly lower edema occurrence was observed after radiosurgery in patients with no history of edema prior to radiosurgery, where the tumor was located in the posterior skull base and where the dosage to the tumor margin was lower than or equal to 14 Gy. Radiosurgery of skull base meningiomas has been proven to be safe and efficient. We consider gamma knife treatment for skull base meningiomas to be the method of choice whenever tumors are within the volume limits and there is no need for an urgent decompressive effect from the open operation.

Gamma knife radiosurgery in neuro-ophthalmology

PURPOSE OF REVIEW

Following technological advances in imaging and dose planning made in the past decade, gamma knife radiosurgery has become more and more an established treatment for a wide range of indications of interest and import to the neuro-ophthalmology community. These areas include cavernous sinus lesions and sellar lesions (for which radiosurgery can be offered as adjuvant or in certain cases as primary treatment), cavernous sinus fistulae, parasellar syndromes, and pituitary tumors.

RECENT FINDINGS

Occurrence of radiation-induced cranial nerve deficits and radiation-induced optic neuropathy are infrequent following radiosurgery to these areas, and perhaps radiation-induced necrosis is less prevalent than in conventional radio therapeutic interventions.

SUMMARY

Gamma knife radiosurgery remains a compelling treatment for lesions of the cavernous sinus, pineal, and sellar regions and offers increasing applicability for ocular conditions such as uveal melanoma and glaucoma.

Image-guided frameless stereotactic biopsy sampling of parasellar lesions. Technical note

Interactive image-guided neuronavigation was used to obtain biopsy specimens of cavernous sinus (CS) tumors via the foramen ovale. In this study the authors demonstrated a minimally invasive approach in the management of these lesions. In four patients, whose ages ranged from 29 to 89 years (mean 61.2 years) and who harbored undefined lesions invading the CS, neuronavigation was used to perform frameless stereotactic fine-needle biopsy sampling through the foramen ovale. The biopsy site was confirmed on postoperative computerized tomography scanning. The frameless technique was accurate in displaying a real-time trajectory of the biopsy needle throughout the procedure. The lesions within the CS were approached precisely and safely. Diagnostic tissue was obtained in all cases and treatment was administered with the aid of stereotactic radiosurgery or fractionated stereotactic radiotherapy. The patients were discharged after an overnight stay with no complications. Neuronavigation is a precise and useful tool for image-guided biopsy sampling of CS tumors via the foramen ovale.

Results of stereotactic radiosurgery in patients with hormone-producing pituitary adenomas: factors associated with endocrine normalization

OBJECT

The goal of this study was to determine factors associated with endocrine normalization after radiosurgery is performed in patients with hormone-producing pituitary adenomas.

METHODS

Between 1990 and 1999, 43 patients with hormone-producing pituitary adenomas underwent radiosurgery: 26 patients with growth hormone (GH)-producing tumors, nine with adrenocorticotrophic hormone-producing tumors, seven with tumors that produced prolactin (PRL) alone, and one with a tumor that secreted both GH and PRL. The median patient age was 42 years. Thirty-seven patients (86%) had undergone surgery earlier and in 30 (70%) there was tumor extension into the cavernous sinus. The product-limit method was used to calculate endocrine normalization while patients were not receiving any hormone-suppressive medication. The median follow-up period after radiosurgery was 36 months (range 12-108 months). In 20 patients (47%) there was normalization of hormone secretion at a median of 14 months (range 2-44 months) after radiosurgery; no correlation was found between tumor type and cure. Actuarial cure rates were 20, 32, and 61% at 1, 2, and 4 years posttreatment. Multivariate analysis demonstrated that the absence of hormone-suppressive medications at the time of radiosurgery (relative risk 8.9, 95% confidence interval [CI] 1.2-68.7, p = 0.04) and maximum radiation doses greater than 40 Gy (relative risk 3.9, 95% CI 1.3-11.7, p = 0.02) correlated with an endocrine cure. A new anterior pituitary deficiency developed in seven patients (16%), temporal lobe necrosis was identified in two patients, an asymptomatic internal carotid artery stenosis was detected in two patients, and unilateral blindness occurred in one patient.

CONCLUSIONS

Radiosurgery provides an endocrine cure for many patients with persistent or recurrent hormone-producing pituitary adenomas. Further study is needed to determine whether pituitary hormone-suppressive medications have a radioprotective effect.

Glossopharyngeal nerve evoked potentials after stimulation of the posterior part of the tongue in dogs

OBJECTIVE

Lower cranial nerve palsy is one of the most critical complications after posterior fossa surgery. However, no established monitoring procedures exist for glossopharyngeal nerve function. Therefore, glossopharyngeal nerve evoked potentials after stimulation of the posterior part of the tongue in dogs was studied to analyze whether glossopharyngeal nerve compound action potentials and evoked potentials are useful in the intraoperative monitoring of patients undergoing brainstem and cerebellopontine angle surgery.

METHODS

Glossopharyngeal nerve action potentials and cortical potentials were evoked by stimulating the posterior part of the tongue in mongrel dogs. The potentials were evoked by supramaximal constant current electrical stimuli delivered with bipolar stainless steel needle electrodes and recorded with silver ball electrodes.

RESULTS

Compound nerve action potentials were recorded from the exposed intracranial portion of the glossopharyngeal nerve. The latency of the initial negative peak of the action potentials was 2.8 +/- 0.6 milliseconds (mean +/- standard deviation; n = 17). Evoked cortical potentials were recorded on the coronal gyrus by stimulating the contralateral side. The latencies of the initial positive peak and negative peak were 20.1 +/- 3.7 and 35.7 +/- 8.2 milliseconds, respectively (n = 6). Ipsilateral tongue stimulation elicited biphasic evoked potentials on the coronal gyrus, which had small amplitudes and delayed latencies. Both compound nerve action potentials and cortical evoked potentials disappeared after sectioning of the glossopharyngeal nerve.

CONCLUSION

The glossopharyngeal nerve action potentials and cortical potentials elicited by the stimulation of the posterior one-third of the tongue can be recorded. These evoked potentials represent a new means for intraoperative monitoring of patients undergoing surgery in the brainstem via the cerebellopontine angle, which involves the lower cranial nerves.

Stereotactic radiosurgery providing long-term tumor control of cavernous sinus meningiomas

OBJECT

To evaluate long-term outcomes of patients who have undergone stereotactic radiosurgery for cavernous sinus meningiomas, the authors retrospectively reviewed their 14-year experience with these cases.

METHODS

One hundred seventy-six patients harbored meningiomas centered within the cavernous sinus. Seventeen patients were lost to follow-up review, leaving 159 analyzable patients, in whom 164 procedures were performed. Seventy-six patients (48%) underwent adjuvant radiosurgery after one or more attempts at surgical resection. Eighty-three patients (52%) underwent primary radiosurgery. Two patients (1%) had previously received fractionated external-beam radiation therapy. Four patients (2%) harbored histologically verified atypical or malignant meningiomas. Conformal multiple isocenter gamma knife surgery was performed. The median dose applied to the tumor margin was 13 Gy. Neurological status improved in 46 patients (29%), remained stable in 99 (62%), and eventually worsened in 14 (9%). Adverse effects of radiation occurred after 11 procedures (6.7%). Tumor volumes decreased in 54 patients (34%), remained stable in 96 (60%), and increased in nine (6%). The actuarial tumor control rate for patients with typical meningiomas was 93.1 +/- 3.3% at both 5 and 10 years. For the 83 patients who underwent radiosurgery as their sole treatment, the actuarial tumor control rate at 5 years was 96.9 +/- 3%.

CONCLUSIONS

Stereotactic radiosurgery provided safe and effective management of cavernous sinus meningiomas. We believe it is the preferred management strategy for tumors of suitable volume (average tumor diameter < or = 3 cm or volume < or = 15 cm3).