[Diagnosis and surgical indications of traumatic brachial plexus lesions from the neurosurgery viewpoint]

The precise preoperative clinical and electrophysiological evaluation of the brachial plexus as well as an exact radiological evaluation are the keystones for the treatment of traumatic injuries of the brachial plexus. Furthermore, surgical management and prognosis of traction injuries of the brachial plexus depend on the accurate diagnosis of root avulsion from the spinal cord. Myelography, myelo-computed tomography and recently magnetic resonance imaging are the main radiological methods for preoperative diagnose of cervical root avulsions. Surgical experience shows that in may cases, extraspinal findings diverge from intradural findings. Consequently, only correlation with the intradural surgical findings will allow us to define the factual accuracy of myelo-CT and MRI studies. Accuracy of the preoperative myelo-CT based diagnosis related to the intraoperative intradural findings was 85% On the other hand, MRI showed an accuracy of only 52%. Therefore, myelo-CT scans with 1 to 3 mm axial slices proves to be the most reliable method to evaluate preoperatively the presence of complete or partial root avulsion in traumatic brachial plexus injuries. However in 15% of the cases preoperative exact radiological diagnosis is unfortunately not reliable. In these special cases intraspinal surgical exposure of the cervical roots will provide the accurate diagnosis of root avulsion. Accurate clinical evaluation and exact assessment of intraspinal root avulsion simplify enormously the decision concerning the choice of donor nerves for transplantation and/or neurotization during brachial plexus surgery.

Direct brainstem recording of auditory evoked potentials during vestibular schwannoma resection: nuclear BAEP recording. Technical note and preliminary results

The usefulness of intraoperative monitoring in cerebellopontine angle surgery should be improved by obtaining faster and stronger brainstem auditory evoked potential (BAEP) responses. A new technique of direct recording at the brainstem has been developed, which is applicable to all tumor sizes. By placing a retractor with electrodes attached to its tip at the cerebellomedullary junction, the authors have recorded BAEP amplitudes that are 10 times greater than those recorded using the conventional technique. Only small sampling numbers (64-256 recordings) are required and are obtained in 5 to 15 seconds. The technique has been applied successfully in 34 patients who underwent vestibular schwannoma resections. It has also been tested in patients with intrameatal-extrameatal meningiomas and in those with vascular compressive disorders; there have been no false results. The advantages of this new technique are: 1) identification of BAEP components is easier and faster; 2) reliable BAEP responses are obtained in some cases in which conventional BAEP responses are lost or severely deformed; and 3) BAEP response deterioration and improvement are recognized earlier than would occur using the conventional technique. This last advantage provides the surgeon with a useful warning at a stage of surgery at which BAEP changes are still temporary and can be reversed. This method is different from other trials of intradural BAEP recordings in three respects: its use is not limited to particular tumor sizes; there is no interference with the surgical process; and, most important, the obtained responses correlate well with those of conventional BAEP responses, probably because the recording site is in the vicinity of the anterior cochlear nucleus. In conclusion, the chances of useful monitoring feedback with adequate adaptation of the microsurgical strategy are improved considerably.

Management of vestibular schwannomas (acoustic neuromas): the value of neurophysiology for evaluation and prediction of auditory function in 420 cases

OBJECTIVE

From 1978 to 1993, 1000 vestibular schwannomas were operated on at the Department of Neurosurgery at Nordstadt Hospital. The goal was to improve the chances of hearing preservation by recording auditory brain stem responses (ABRs). ABRs can be used for preoperative classification of cochlear nerve impairment and for prediction of the chances of hearing preservation.

PATIENTS AND METHODS

In addition to the previously described audiometric testing, the patients underwent perioperative and intraoperative bilateral ABR recording at 100-dB condensation and rarefaction click stimulation. The classification system of five types of ABRs, as presented before, is based on the presence and on the latencies of Waves I, III, and V, with a special emphasis on Wave III's representing the activity of the first brain stem nuclei within the auditory pathway. According to an analysis of 420 preoperative ABRs, in case of a preoperative Type 1 or 2, the rate of hearing preservation is 80%.

DISCUSSION

In the case of good clinical and audiometric hearing, a severely deteriorated ABR is mostly an indicator of severe nerve compression and adhesion by the tumor. In view of subsequently reported experiences with intraoperative ABR monitoring, the value of the presented system emphasizing the importance of Wave III is stressed and discussed with other views in the literature. The criteria presented here are not designed for recognition of retrocochlear disease but aim for evaluation of the state of the auditory nerve and its perspective.

CONCLUSION

By the presented classification of ABR Type B1 through B5, preoperative prediction of the likelihood of hearing preservation is improved.

Management of 1000 vestibular schwannomas (acoustic neuromas): the facial nerve--preservation and restitution of function

OBJECTIVE

Although the rate of reported facial nerve preservation after surgery for vestibular schwannomas continuously increases, facial nerve paresis or paralysis is a frequent postsurgical sequelae of major concern. The major goal of this study was to define criteria for the right indication, timing, and type of therapy for patients with palsies despite anatomic nerve continuity and those with loss of anatomic continuity.

METHODS

One thousand vestibular schwannomas were surgically treated at the Department of Neurosurgery at Nordstadt Hospital from 1978 to 1993. Of 979 cases of complete removal and 21 cases of deliberately partial removal, the facial nerve was anatomically preserved in 929 cases (93%). The rate of preservation is increasing, as is evidenced in the most recent cases, and preservation is supported by special electrophysiological monitoring. The facial nerve was anatomically severed in 60 cases (6%). It was anatomically lost in previous operations that were performed elsewhere in 11 cases (1%). In case of nerve discontinuity (42 cases), immediate nerve reconstruction by one of three available intracranial procedures (within the cerebellopontine angle, intracranial-intratemporal, intracranial-extracranial) was performed in the same surgical setting. In case of loss of the proximal facial nerve stump at the brain stem, early reanimation by combination with the hypoglossal nerve was achieved in most patients within weeks after tumor surgery. In a few patients with anatomic nerve continuity but absence of reinnervation for 10 to 12 months, a hypoglossal-facial combination was applied. All the patients with partial or with complete palsies were treated in a special follow-up program of regular controls and of modulation of physiotherapeutic treatment every 3 to 6 months.

RESULTS

In intracranial nerve reconstruction at the cerebellopontine angle, 61 to 70% of patients regained complete eye closure and an overall result equivalent to House-Brackmann Grade 3. Hypoglossal-facial reanimation led to Grade 3 in 79%. The duration between the onset of paralysis and the reconstructive procedure is decisive for the quality of the outcome. These data are discussed in view of other treatment options and certain parameters influencing outcome.

CONCLUSIONS

This management contains three major principles as follows: 1) preservation of facial nerve continuity in function by the aid of intraoperative monitoring, 2) early nerve reconstruction in case of lost continuity, and 3) scheduled follow-up program for all patients with incomplete or complete palsies.

Management of vestibular schwannomas (acoustic neuromas): auditory and facial nerve function after resection of 120 vestibular schwannomas in patients with neurofibromatosis 2

OBJECTIVE

Vestibular schwannomas (VSs) affect young patients with Neurofibromatosis 2 (NF-2) and cause very serious problems for hearing, facial expression, and brain stem function. Our objective was to determine a therapy concept for the right timing and indication of neurosurgical therapy.

METHODS

In 1000 consecutive VS resections, 120 tumors in 82 patients with NF-2 were surgically treated by the same surgeon (MS) at the Department of Neurosurgery at Nordstadt Hospital from 1978 to 1993. The mean age of the patients was 27.5 years. Sixty tumors were surgically treated in 41 male patients, and 60 tumors were surgically treated in 41 female patients. Bilateral tumor resection was performed in 38 patients (76 operations, after previous partial surgery in 15 cases elsewhere), and unilateral operations were performed in 44 patients, 5 of whom had undergone ipsi- or contralateral surgery that was performed elsewhere. The operative and clinical findings are evaluated and compared with the data of patients without NF-2.

RESULTS

In 105 cases, complete tumor resections were achieved. In 15 cases, deliberate subtotal resections were performed. These were for brain stem decompression in 4 cases and for hearing preservation in the last hearing ear in 11 cases, with successful preservation in 8 of the 11. Pre- and postoperative hearing rates were higher in male than in female patients (70% in male versus 65% in female patients before surgery and 40.5 versus 31%, respectively, after surgery). Hearing was preserved in 29 of 81 ears (36%). The rate of preservation was 24% in cases of large tumors and 57% in cases of small tumors (<30 mm). Twenty-one of 82 patients (26%) were bilaterally deaf before surgery. Twenty-five patients had uni- or bilateral hearing after surgery (i.e., 41 % of those with preoperative hearing or 30.5% of the whole group). Anatomic facial nerve preservation was achieved in 85%. The facial nerve was reconstructed intracranially at the cerebellopontine angle by sural grafting in 17 cases and by hypoglossal-facial reanimation in 5. Two deaths occurred 1 and 3 months postsurgically as a result of malignant tumor growth with brain stem dysfunction and respiratory problems. In summary, for patients with NF-2, the presentation ages are lower, tumor progression is faster, the chances of anatomic and functional nerve preservation are lower, the chances of good outcomes are best when surgery is performed early and when there is good preoperative hearing function, and the danger of sudden hearing loss is higher. The chances and danger often differ from side to side among individual patients.

CONCLUSION

The indication and the timing of tumor resections are in some respects different from normal VS handling and are dependent on the tumor extension and related necessity of brain stem decompression and on the auditory function. As an optimal goal, completeness of resection with functional cochlear nerve preservation is formulated, and as an acceptable compromise, subtotal microsurgical resection with functional cochlear nerve preservation in the last hearing ear is suggested.

Management of vestibular schwannomas (acoustic neuromas): radiological features in 202 cases--their value for diagnosis and their predictive importance

OBJECTIVE

Tumor-induced bony and soft tissue findings might reflect, in part, the biological characteristics of vestibular schwannomas and could predict clinical findings. In addition, the role of the individual anatomic conditions of the posterior fossa is of interest to the surgeon.

METHODS

Of 1000 vestibular schwannomas treated surgically at the neurosurgical department at Nordstadt Hospital, 202 cases, which were consecutively investigated at the same computed tomography (CT) unit and using the same technique (high-resolution CT at bone windows before and after surgery, contrast-enhanced high-resolution CT before surgery, and native high-resolution CT after surgery), were evaluated for special radiological features. Evaluation included, in 103 cases, anatomic parameters of the petrous bone and posterior fossa cavity and, in 202 cases, tumor-induced changes of bony structures, tumor relations with bony structures and with neural structures, and postoperative findings of bony structures and of neural tissues. These radiological parameters and the related clinical pre- and postoperative findings were transferred to a database for statistical evaluation of their positive or negative correlations, i.e., for their reliability in diagnosis and their importance in predicting postsurgical outcome.

RESULTS

As important parameters, the following could be identified. The length of the posterior auditory canal wall and the interear difference of the maximum porus width both correlate with the degree of preoperative hearing deterioration (P < 0.05). The extent of the widening of the internal auditory canal is of predictive importance for the chances of postoperative hearing preservation or hearing loss (P < 0.01). The extent of tumor growth anterior and caudal to the internal auditory canal in large tumors is of significant importance for prediction of postoperative hearing function (P < 0.05). The tumor extension in all directions and the extent of cystic tumor components correlate with the pre- and postoperative function of the facial and cochlear nerves. The positions of the labyrinthine structures and their geographical relations to the fundus and the sigmoid sinus and, thereby, to the suboccipital route, enable reliable calculations of the danger of labyrinthine destruction and help improve the planning of the surgical strategy.

DISCUSSION AND CONCLUSIONS

In addition to the importance for surgical planning, preoperative bone window CT and contrast-enhanced images offer the opportunity to identify traits of tumor biology, such as bony destruction of the internal auditory canal, tumor shape and cyst formation, and aspects with predictive importance for postoperative outcome. The average size for hearing preservation in tumors was 14.5 x 16.5 x 11.8 mm (coronal x sagittal x axial). The recent finding (8) of a higher presentation age in female patients has an apparently anatomic basis, which is a relatively larger internal auditory meatus.

Management of vestibular schwannomas (acoustic neuromas): the value of neurophysiology for intraoperative monitoring of auditory function in 200 cases

OBJECTIVE

The present study investigated the significance of the presence or absence of auditory brain stem response (ABR) Waves I, III, and V as functional representatives of the cochlea, the nucleus cochlearis, and the colliculus inferior, respectively, and attempted to identify the microsurgical maneuvers that were especially likely to cause isolated or combined component losses and subsequent hearing losses.

METHODS

Based on the previously described ABR classification system, 201 patients with preserved Waves I, III, and V or Waves I and V were investigated for the peak latencies and amplitudes of the waves at 15 defined microsurgical stages. Analysis was performed with respect to the presence or absence of ABR components during specific microsurgical actions and the related danger of deafness.

RESULTS

Temporary or permanent losses of Waves V, I, and III occurred with 21, 27, and 29% of surgical actions, respectively, leading to deafness in 65 to 78% of the patients. Wave III disappearance was identified as the earliest and most sensitive sign. Wave V loss was usually preceded by disappearances of Waves I and III. During the most dangerous actions (drilling, pulling downward, medially, or laterally, and direct nerve manipulation), special attention ws paid to deterioration of Wave-III and then Wave I; if impairment was seen, intermittent breaks or changes in the type or site of microsurgical action were used to enable wave recovery. Acute, simultaneous, and permanent loss of all waves occurred in 27.5% of postoperatively deaf patients, whereas stepwise wave deterioration and losses occurred in 72.5%.

CONCLUSION

Useful (in-time) recognition of significant waveform changes is possible and enables a change of microsurgical maneuvers to favor ABR recovery.

Cystic meningiomas resembling glial tumors

BACKGROUND

Meningiomas can be associated with peripheral or intratumoral cysts. Meningiomas with intratumoral cysts, also called "true cystic" meningiomas, are rare and can frequently be confused with glial or metastatic tumors.

METHODS

We report three cases of "true cystic" meningiomas and discuss the preoperative evaluation, etiology, and surgical treatment of these cystic lesions with reference to the literature.

RESULTS

Magnetic resonance imaging (MRI) and computed tomography (CT) studies usually display a cystic lesion close to the dura with or without enhancement of the cyst wall. Multiplanar MRI scans are very useful to show the presence of a solid tumor or some dural enhancement. Some cases of "true cystic" meningiomas however, are still erroneously preoperatively diagnosed. Complete surgical removal of the tumors and of the entire cyst wall was performed in our cases. Despite the absence of a typical ring enhancement of the cystic lesion in two cases, histopathologic studies displayed the presence of tumor cells on the cyst wall of both cases.

CONCLUSIONS

Tumor cells can be present on the cyst wall and therefore can be one of the causes of tumor recurrence if not totally removed. Accurate preoperative radiologic diagnosis (multiplanar MR images) and intraoperative histopathologic studies are fundamental in that they will definitely influence the surgical strategy and outcome.

Management of 1000 vestibular schwannomas (acoustic neuromas): hearing function in 1000 tumor resections

OBJECTIVE

The realistic chances of hearing preservation and the comparability of international results on hearing preservation in complete microsurgical vestibular schwannoma resections were the focus of this study in a large patient population treated by uniform principles.

METHODS

One thousand vestibular schwannomas were operated on at Nordstadt Neurosurgical Department, from 1978 to 1993, by the senior surgeon (MS). There were 1000 tumors in 962 patients, i.e., 880 patients with unilateral tumors and 82 patients operated on for bilateral tumors in neurofibromatosis-2 (120 cases). Preservation of the cochlear nerve was attempted whenever possible. The audiometric data were analyzed by the Nordstadt classification system and graded in steps of 30 dB by audiometry and in steps of 10 to 30% by speech discrimination; for comparability, the data were also evaluated by the criteria of Gardner, Shelton, and House, and they were assessed in relation to the Hannover tumor extension grading system.

RESULTS

Anatomic cochlear nerve preservation was achieved in 682 of 1000 cases (68%), as well as in some preoperatively deaf patients, a very few of whom regained some hearing. Of a total of 732 cases with some preoperative hearing, anatomic cochlear nerve preservation was achieved in 580 cases (79%) and functional cochlear nerve preservation in 289 (39.5%); analysis over time revealed an actual preservation rate of 47% in the most recent 200 cases. Specific factors, such as gender, tumor extension, preoperative hearing quality, and symptom duration, were investigated for their predictive value for hearing preservation. Male gender, small to medium tumor size (mainly extending within the cerebellopontine cistern; Classes T2 and T3), good to moderate hearing (up to 40-dB loss), and short duration of hypoacusis (< 1.5 yr) or of vestibular disturbances (< 0.7 yr) were advantageous factors, with chances of hearing preservation between 47 and 88%.

CONCLUSION

Functional cochlear nerve preservation in complete microsurgical resection should belong to the contemporary standard of treatment goals.

Treatment of syringomyelia associated with arachnoid scarring caused by arachnoiditis or trauma

The authors conducted a retrospective study of 107 patients treated for syringomyelia associated with arachnoid scarring between 1976 and 1995 at the Departments of Neurosurgery at the Nordstadt Hospital in Hannover, Germany, and the University of California in Los Angeles, California. Twenty-nine patients have not been surgically treated to date because of their stable neurological status. Seventy-eight patients with progressive neurological deficits underwent a total of 121 surgical procedures and were followed for a mean period of 32 (+/- 37) months. All patients demonstrated arachnoid scarring at a level close to the syrinx. In 52 patients the arachnoid scarring was related to spinal trauma, whereas 55 had no history of trauma and developed arachnoid scarring was a result of an inflammatory reaction. Of these, 15 patients had undergone intradural surgery, eight had suffered from spinal meningitis, three had undergone peridural anesthesia, and one each presented with a history of osteomyelitis, spondylodiscitis, and subarachnoid hemorrhage. No obvious cause for the inflammatory reaction resulting in arachnoid scarring could be ascertained for the remaining 26 patients. The postoperative neurological outcome correlated with the severity of arachnoid pathology and the type of surgery performed. Shunting of the syrinx to the subarachnoid, pleural, or peritoneal cavity was associated with recurrence rates of 92% and 100% for focal and extensive scarring, respectively. Successful long-term management of the syrinx required microsurgical dissection of the arachnoid scar and decompression of the subarachnoid space with a fascia lata graft. This operation stabilized the preoperative progressive neurological course in 83% of patients with a focal arachnoid scar. For patients with extensive arachnoid scarring over multiple spinal levels or after previous surgery, clinical stabilization was achieved in only 17% with this technique.

Surgical management of craniopharyngiomas: a review

Craniopharyngiomas are uncommon benign intracranial tumors that still represent a task in management. Controversy exists concerning the treatment of choice for these tumors. Radical surgery, subtotal resection combined with radiotherapy, or primary irradiation are the frequent treatment modalities. Although an increasing number of reports have appeared stressing the role of primary radiation for these tumors, radical surgery still represents the treatment of choice in most cases, since craniopharyngioma is a benign tumor and many affected patients are at a young age. In this article the authors review different aspects of pathology, clinical presentation, radiology, and management of the craniopharyngiomas. Common surgical approaches are described and both preoperative and postoperative management are outlined.

Management of 1000 vestibular schwannomas (acoustic neuromas): surgical management and results with an emphasis on complications and how to avoid them

OBJECTIVE

To identify the actual benefits and persisting problems in treating vestibular schwannomas by the suboccipital approach, the results and complications in a consecutive series of 1000 tumors surgically treated by the senior author were analyzed and compared with experiences involving other treatment modalities.

METHODS

Pre- and postoperative clinical statuses were determined and radiological and surgical findings were collected and evaluated in a large database for 962 patients undergoing 1000 vestibular schwannoma operations at Nordstadt's neurosurgical department from 1978 to 1993.

RESULTS

By the suboccipital transmeatal approach, 979 tumors were completely removed; in 21 cases, deliberate partial removal was performed either in severely ill patients for decompression of the brain stem or in an attempt to preserve hearing in the last hearing ear. Anatomic preservation of the facial nerve was achieved in 93% of the patients and of the cochlear nerve in 68%. Major neurological complications included 1 case of tetraparesis, 10 cases of hemiparesis, and caudal cranial nerve palsies in 5.5% of the cases. Surgical complications included hematomas in 2.2% of the cases, cerebrospinal fluid fistulas in 9.2%, hydrocephalus in 2.3%, bacterial meningitis in 1.2%, and wound revisions in 1.1%. There were 11 deaths occurring at 2 to 69 days postoperatively (1.1%). The techniques that were developed for avoidance of complications are reported. The analysis identifies preexisting severe general and/or neurological morbidity, cystic tumor formation, and major caudal cranial nerve deficits as relevant risk factors.

CONCLUSION

The current treatment options of complete tumor resection with ongoing reduction of morbidity are well fulfilled by the suboccipital approach. By careful patient selection, the mortality rate should be further reduced to below 1%.

Diagnosis of root avulsions in traumatic brachial plexus injuries: value of computerized tomography myelography and magnetic resonance imaging

Surgical management and prognosis of traction injuries of the brachial plexus depend on the accurate diagnosis of root avulsion from the spinal cord. Myelography, computerized tomography (CT) myelography, and recently magnetic resonance (MR) imaging have become the main radiological methods for preoperative diagnosis of cervical root avulsions. Most of the previous studies on the accuracy of CT myelography and MR imaging studies have correlated the radiological findings with the extraspinal surgical findings at brachial plexus surgery. Surgical experience shows that in many cases extraspinal findings diverge from intradural determinations. Consequently, only correlation with the intradural surgical findings will allow assessment of the factual accuracy of CT myelography and MR imaging studies. In a prospective study, 135 cervical roots (C5-8) were evaluated by CT myelography and/or MR imaging and further explored intradurally via a hemilaminectomy. The accuracy of the preoperative CT myelography-based diagnosis in relation to the intraoperative findings was 85%. On the other hand, MR imaging demonstrated an accuracy of only 52%. The most common reasons for false-positive or false-negative findings were: 1) partial rootlet avulsion; 2) intradural fibrosis; and 3) dural cystic lesions. Computerized tomography myelography scans using 1- to 3-mm axial slices prove to be the most reliable method to evaluate preoperatively the presence of complete or partial root avulsion in traumatic brachial plexus injuries. Because extradural judgment of cervical root avulsion can be unreliable, accurate assessment of intraspinal root avulsion enormously simplifies the decision concerning the choice of donor nerves for transplantation and/or neurotization during brachial plexus surgery.

Management of 1000 vestibular schwannomas (acoustic neuromas): clinical presentation

OBJECTIVE

Despite good knowledge of the key symptoms of vestibular schwannomas and their significance for surgical results, the evolution of symptoms and signs and their relation to tumor extension still need thorough investigation.

METHODS

From 1978 to 1993, operations were performed by the same surgeon (M.S.) on 1000 vestibular schwannomas at the Neurosurgical Department of Nordstadt Hospital. The vestibular schwannomas were diagnosed in 962 patients, including 522 female patients (54%) and 440 male patients (46%); the mean age was significantly higher in female patients (47.6 yr) than in men (45.2 yr). We focused our analysis on the incidence of subjective disturbances versus objective morbidity, on the sequence of symptom onset, and on symptom duration and symptomatology versus tumor size and extension.

RESULTS

The most frequent clinical symptoms were disturbances of the acoustic (95%), vestibular (61%), trigeminal (9%), and facial (6%) nerves. Symptom duration was 3.7 years for hearing loss, 1.9 years for facial paresis, and 1.3 years for trigeminal disturbances. Symptom incidence and duration did not strictly correlate with tumor size. Key symptoms of various tumor extension classes precipitated the diagnosis, such as trigeminal disturbances in large tumors with brain stem compression or tinnitus in small neuromas. In cases of trigeminal or facial nerve symptoms, the overall duration of symptomatology was much shorter. According to the subjective perception of the patients, between only one- and two-thirds of nerve disturbances were noticed. Patients with preoperative deafness had become deaf either chronically (23%) or suddenly (3%); even in cases of moderate hearing deficit that lasts a long time, deafness can occur suddenly. The rate of tinnitus was higher in hearing than in deaf patients; however, deafness does not mean relief from tinnitus, because this symptom persists in 46% of preoperatively deaf patients. Vestibular disturbances most often occur as some unsteadiness while walking or as vertigo, and the symptoms frequently are fluctuating, not constant.

CONCLUSION

Differences in tumor biology can be underestimated and are not visible on radiological scans. For example, intrameatal tumors, despite their small size, present with a duration of symptoms that is representative of the larger tumors and are most frequently associated with vestibular symptoms and with tinnitus. Large tumors with brain stem compression present with relatively shorter symptom durations and at a younger age; both factors are suggestive of especially fast tumor growth. The clinical findings presented in this study promote new consideration of the dynamics of tumor growth and of the affected neural tissues.