Minimally invasive medial supraorbital, combined subfrontal-interhemispheric approach to the anterior communicating artery complex-a cadaveric study.

INTRODUCTION: In selected cases, microsurgical clipping remains a valuable treatment alternative to endovascular occlusion of anterior communicating artery (AComA) aneurysms. Their clipping is challenging and carries a risk of postsurgical cognitive impairment. We evaluate the microsurgical anatomy of a new, minimally invasive combined interhemispheric-subfrontal approach to the AComA complex via a medial supraorbital craniotomy. METHODS: In this descriptive anatomic study, four alcohol-embedded, silicon-injected human cadaver heads were used. In each of the two cadavers, the AComA complex was approached from either the right or left side. An operating microscope and standard microsurgical instruments were used. RESULTS: After a medial eyebrow incision, a medial supraorbital minicraniotomy was performed. The frontal sinus was opened and cranialized. Following the dural opening, a subfrontal arachnoid dissection was performed to identify the optico-carotid complex. By following the A1 segment, a low-lying AComA complex could be visualized. Shifting the corridor towards the midline enabled an interhemispheric dissection. This dissection resulted in a wide superior-inferior corridor. Higher-lying AComA complexes could also be visualized. The achieved exposure of the AComA complex would allow safe dissection and clipping of low- and high-lying AComA aneurysms, with minimal retraction and preservation of the surrounding anatomical structures, in particular the perforators. CONCLUSIONS: We demonstrate the anatomy of a novel approach for surgical clipping of AComA aneurysms. Our study suggests that this approach provides good exposure without concomitant structural and vascular injury and thus might reduce the risk of procedure-related morbidity.

Intraoperative neurophysiologic monitoring for intramedullary spinal-cord tumor surgery.

During resection of intramedullary spinal-cord tumors intraoperative neurophysiological monitoring has become a true surgical technology. Motor evoked potentials are the most important modality for this purpose. Its use requires neurophysiological expertise from the surgeon, and a monitoring team in place able to handle the necessary equipment. Motor potentials are evoked by transcranial electrical motor cortex stimulation. A "single stimulus technique" evokes D-waves recorded from the spinal cord. The "multipulse (or train) stimulation technique" evokes electromyographic responses in peripheral muscles. These are optimally recorded from the thenar, hypothenar, tibialis anterior, and flexor hallucis brevis muscles, which are known to have strong pyramidal innervation. D-wave monitoring looks primarily at the peak-to-peak amplitude. When monitoring muscle MEPs, the presence or absence of the response irrespective of stimulation intensity is the important parameter. Preparations for neurophysiological monitoring fit quite well into a neurosurgical operating room environment. Recording and interpretation of MEPs is fast and straightforward. Pre- and postoperative clinical motor findings correlate with intraoperative MEP results. Thus correct prediction of the clinical status at a given time during surgery is possible with a very high certainty. The sensitivity of muscle MEPs for postoperative motor deficits is nearly 100%, its specificity is about 90%. Thus MEP data indeed reflect the clinical "reality". Present and stable recordings document intact motor pathways and allow the surgeon to confidently proceed with a tumor resection. Loss of muscle MEPs and/or decrease of the D-wave amplitude constitutes a "window of warning". It reflects a pattern of MEP change indicating a reversible injury to the essential motor pathways. Using this information, the surgical strategy can be adapted before irreversible neurological damage is caused by the surgical manipulation. Such adaptation comprises simply waiting for the recordings to spontaneously improve again, irrigating with warm saline solution to wash out blocking potassium. Other measures include the elevation of mean arterial pressure to improve local perfusion. Even staged resection can be considered if intraoperative measures do not sufficiently improve the recordings.

Use of microsurgical laser in paediatric surgery and paediatric neurosurgery.

Our descriptive technical report on 7 children describes the microsurgical laser scalpel as an useful tool for removal of firm and soft lesions from a variety of delicate tissues. It combines precise atraumatic tissue dissection with immediate hemostasis while having no adverse side effects on adjacent and neighbouring tissues even through a limited surgical access.

Foreign body reaction to hemostatic materials mimicking recurrent brain tumor. Report of three cases.

Chemical agents routinely used in neurosurgery to achieve intraoperative hemostasis can cause a foreign body reaction, which appears on magnetic resonance (MR) images to be indistinguishable from recurrent tumor. Clinical and/or imaging evidence of progression of disease early after surgical resection or during aggressive treatment may actually be distinct features of granuloma in these circumstances. A series of three cases was retrospectively analyzed for clinical, imaging, surgical, and pathological findings, and the consequences they held for further disease management. All patients were boys (3, 3, and 6 years of age, respectively) and all harbored primitive neuroectodermal tumors. Two tumors were located in the posterior fossa and one was located in the right parietal lobe. Two boys exhibited clinical symptoms, which were unexpected under the circumstances and prompted new imaging studies. One patient was asymptomatic and imaging was performed at planned routine time intervals. The MR images revealed circumscribed, streaky enhancement in the resection cavity that was suggestive of recurrent disease. This occurred 2 to 7 months after the first surgery. At repeated surgery, the resected material had the macroscopic appearance of gelatin sponge in one case and firm scar tissue in the other cases. Histological analysis revealed foreign body granulomas in the resected material, with Gelfoam or Surgicel as the underlying cause. No recurrent tumor was found and the second surgery resulted in imaging-confirmed complete resection in all three patients. Because recurrent disease was absent, the patients continued to participate in their original treatment protocols. All patients remain free from disease 34, 32, and 19 months after the first operation, respectively. During or after treatment for a central nervous system neoplasm, if unexpected clinical or imaging evidence of recurrence is found, a second-look operation may be necessary to determine the true nature of the findings. If the resection yields recurrent tumor, additional appropriate oncological treatment is warranted, but if a foreign body reaction is found, potentially harmful therapy can be withheld or postponed.

Intraspinal clear cell meningioma: diagnosis and management: report of two cases.

OBJECTIVE AND IMPORTANCE: Intraspinal clear cell meningioma is a rare morphological variant of meningioma. Only 13 case reports are found in the literature; therefore, no management strategy has been defined for this tumor type. This article describes two patients, reviews the literature, and proposes a treatment plan for clear cell meningioma. CLINICAL PRESENTATION: Two female patients, 22 months and 8 years of age, respectively, presented with localized neck and leg pain that limited their ability to walk. Magnetic resonance imaging revealed intradural tumors, a cervical intramedullary neoplasm in the younger patient, and a cauda equina tumor in the older child. INTERVENTION: Both patients underwent radical resection of their intradural tumor. Both tumors, however, recurred shortly (5 and 6 mo) after the initial operation. During the second operation, a radical removal was performed on each patient. Both patients received adjuvant radiotherapy. In addition, the younger patient developed posterior fossa metastasis 20 months after intraspinal surgery. CONCLUSION: Intraspinal clear cell meningiomas are very uncommon tumors. The clinical course in our two patients supports the reported 40% recurrence rate within 15 months. These tumors also can disseminate within the central nervous system. We recommend serial imaging studies every 3 months. For recurrent tumors, we recommend localized radiation therapy after reoperation.

Treatment of Chiari I malformation in patients with and without syringomyelia: a consecutive series of 66 cases.

OBJECT: The authors describe the results of performing a standard posterior craniovertebral decompression and placement, if indicated, of a syringosubarachnoid shunt for the treatment of patients with Chiari I malformation with and without syringomyelia. METHODS: This is a retrospectively analyzed consecutive series of 66 patients (mean patient age 15 years, range 1-53 years). The uniform posterior craniovertebral decompression consisted of a small suboccipital craniectomy, a C-1 laminectomy, microsurgical reduction of the cerebellar tonsils, and dural closure with a synthetic dural graft to increase the cerebrospinal fluid space at the craniocervical junction. The presence of a large syrinx, with significant thinning of the spinal cord tissue and obliteration of the spinal subarachnoid space, particularly when combined with syrinx-related symptoms, was an indication for the placement of a syringosubarachnoid shunt. In 32 patients Chiari I malformation alone was present, and 34 in patients it was present in combination with syringomyelia. Clinical findings included pain, neurological deficits, and spinal deformity. The presence of syringomyelia was significantly associated with the presence of scoliosis (odds ratio 74.4 [95% confidence interval 8.894-622.4]). All patients underwent a posterior craniovertebral decompression procedure. In 22 of the 34 patients with syringomyelia a syringosubarachnoid shunt was also placed. The mean follow-up period was 24 months (range 3-95 months). Excellent outcome was achieved in 54 patients (82%) and good outcome in 12 (18%). In no patient were symptoms unchanged or worse at follow-up examination, including four patients who initially required a second operation for persistent syringomyelia. Pain was more likely to resolve than sensory and motor deficits after decompressive surgery. Radiological examination revealed normalization of tonsillar position in all patients. The syrinx had disappeared in 15 cases, was decreased in size in 17, and remained unchanged in two. CONCLUSIONS: Posterior craniovertebral decompression and selective placement of a syringosubarachnoid shunt in patients with Chiari I malformation and syringomyelia is an effective and safe treatment. Primary placement of a shunt in the presence of a sufficiently large syrinx appears to be beneficial. The question of if and when to place a shunt, however, requires further, preferably prospective, investigation.

Infrasellar craniopharyngiomas: case report and review of the literature.

Although craniopharyngiomas account for a large percentage of pediatric intracranial tumors, there is a bimodal age distribution. Most of these neoplasms are suprasellar or sellar in location. In this report we describe an unusual case of an infrasellar craniopharyngioma in a child. Only four previous cases of infrasellar craniopharyngiomas with no sellar involvement have been described. Infrasellar craniopharyngiomas are part of the continuum representing intracranial craniopharyngiomas and ameloblastomas of the jaw. A transnasal endoscopic biopsy was performed with a preliminary diagnosis of craniopharyngioma. The patient then underwent a radical resection of the infrasellar tumor via a subfrontal transbasal approach. This case illustrates a rare and unusual location for a craniopharyngioma. Craniopharyngiomas should be considered in the differential diagnosis of infrasellar neoplasms. Infrasellar craniopharyngiomas compromise part of the spectrum of tumors originating from enamel-forming neural crest cells.

Transdural cauda equina incarceration after microsurgical lumbar discectomy: case report.

OBJECTIVE AND IMPORTANCE: Complications usually occur when they are least expected. We present an unusual case of nerve entrapment after microsurgical discectomy. CLINICAL PRESENTATION: A patient undergoing uneventful first lumbar microsurgical discectomy developed severe back and leg pain and a progressive neurological deficit during the first postoperative night. Herniation of cauda equina nerve roots had occurred through an unnoticed minimal defect in the dura, which had not caused cerebrospinal fluid leakage. The roots were incarcerated and swollen, and they filled the space of the resected nucleus pulposus. It was presumed that elevation of intra-abdominal pressure and consequent increased intraspinal pressure during extubation led to the herniation of arachnoid and cauda equina roots. The nerve roots were then trapped and incarcerated in the manner of bowel loops in an abdominal wall hernia. INTERVENTION: During reoperation, the nerve roots were repositioned into the dural sac. The patient recovered without further complications and without long-term sequelae. CONCLUSION: All dural tears that occur during intraspinal surgery, even if they are small and the arachnoid is intact, should be closed with stitches or at a minimum with a patch of muscle or gelatin sponge with fibrin glue. Care should be taken to avoid increased intra-abdominal pressure during extubation. Excessive pain and progressive neurological dysfunction occurring shortly after microsurgical lumbar discectomy or any intraspinal procedure is indicative of possible hemorrhage with subsequent compression of nerve roots. The case reported here provides anecdotal evidence that this situation can also be caused by a herniation of cauda equina nerve roots through a small dural defect that was not evident during the initial operation.

Motor-evoked potential monitoring for intramedullary spinal cord tumor surgery: correlation of clinical and neurophysiological data in a series of 100 consecutive procedures.

Resection of intramedullary spinal cord tumors carries a high risk for surgical damage to the motor pathways. This surgery is therefore optimal for testing the performance of intraoperative motor evoked potential (MEP) monitoring. This report attempts to provide evidence for the accurate representation of patients' pre- and postoperative motor status by combined epidural and muscle MEP monitoring during intramedullary surgery. The authors used transcranial electrical motor cortex stimulation to elicit MEPs, which were recorded from the spinal cord (with an epidural electrode) and from limb target muscles (thenar, anterior tibial) with needle electrodes. The amplitude of the epidural MEPs and the presence or absence of muscle MEPs were the parameters for MEP interpretation. A retrospective analysis was performed on data from the resection of 100 consecutive intramedullary tumors and MEP data were compared with the pre- and postoperative motor status. Intraoperative monitoring was feasible in all patients without severe preoperative motor deficits. Preoperatively paraplegic patients had no recordable MEPs. The sensitivity of muscle MEPs to detect postoperative motor deficits was 100% and its specificity was 91%. There was no instance in which a patient with stable MEPs developed a motor deficit postoperatively. Intraoperative MEPs adequately represented the motor status of patients undergoing surgery for intramedullary tumors. Because deterioration of the motor status was transient in all cases, it can be considered that impairment of the functional integrity of the motor pathways was detected before permanent deficits occurred.

Motor evoked potentials predicting early recovery from paraparesis after embolisation of a spinal dural arteriovenous fistula.

SUMMARY: Spinal dural arteriovenous malformation is an increasingly diagnosed cause of ischaemic myelopathy. Though routine intraoperative monitoring has been demonstrated to be of benefit in the endovascular treatment of these lesions, its predictive value has not been well documented. We present the case of an elderly woman with progressive spastic paraparesis who demonstrated marked improvement in limb muscle motor evoked potentials of the lower extremities immediately following endovascular occlusion of the lesion. The patient subsequently showed improvement in strength, sensation and sphincter control.

Intraoperative spinal cord monitoring for intramedullary surgery: an essential adjunct.

Intraoperative monitoring of the functional integrity of the spinal cord during removal of intramedullary spinal cord lesions is an aid in intraoperative decision making and a primary tool for the prediction of neurological outcome. Motor evoked potential monitoring has become the neurophysiological monitoring technique of choice for that purpose. In the senior author's experience with over 130 pediatric patients suffering from intramedullary spinal cord tumors, the neurophysiological data of both motor and sensory evoked potentials was utilized in an integrative fashion. Motor evoked potentials, elicited with single transcranial electrical stimuli and recorded directly from the spinal cord with an electrode in the spinal epidural space, reflect the functional integrity of the corticospinal tract. Motor evoked potentials, elicited with a short train of transcranial electrical stimuli and recorded from limb muscles, reflect the functional integrity of the motor system from the cerebral cortex/white matter to beyond the neuromuscular junction. Both epidural and muscle motor evoked potentials correlated closely with postoperative neurological function. Both techniques provide fast, practical and reliable information on the functional integrity of the motor tracts of the spinal cord. No complications attributable to stimulation or recording occurred. Over time both the technique's reliable power of predicting clinical outcome and its practical versatility have altered the surgical approach in that gross total resections are more readily attempted as long as motor evoked potential data indicate the intact functional integrity of the corticospinal tract. This monitoring technique unquestionably had a favorable impact on neurological outcome.

[Tethered spinal cord syndrome in adults]. / Das Tethered-spinal-cord Syndrom beim Erwachsenen.

The tethered spinal cord syndrome is more often encountered in children, but does also occur in adults. Its clinical spectrum comprises low back pain, neurological deficits such as distal motor weakness and trophic and sensory disturbances in the legs, urological symptoms and such musculoskeletal signs as scoliosis or foot deformities. In addition, cutaneous lesions or subcutaneous lipomas in the lumbosacral region may be indirect signs of an intraspinal pathology. This consists in a tight, thickened and sometimes shortened filum terminale, an intraspinal lipoma, intradural scar formation or other lesions that lead to conus fixation. The common mechanism of injury of these types of pathologies is an impairment of longitudinal movement of the spinal cord, especially the conus medullaris, which subsequently leads to chronic local ischemia. Diagnosis is most readily achieved by magnetic resonance imaging. Treatment is aimed at the restoration of cord mobility by means of microsurgical release of the conus, the cauda equina and the filum terminale with the aid of cauda equina neuromonitoring. Further progression can be effectively halted; in fact almost half of the patient actually improve. Therefore, every patients presenting with the clinical diagnosis of tethered cord syndrome should be offered specialized surgical treatment.

The mapping and continuous monitoring of the intrinsic motor nuclei during brain stem surgery.

A comprehensive technique was developed for continuous electrophysiological monitoring of intrinsic brain stem motor function during surgery to remove space-occupying lesions in the fourth ventricle and brain stem. The technique is analogous to that used during surgery in the cerebellopontine angle; motor nuclei and peripheral pontine fiber tracts of Cranial Nerves III-XII are identified by the electrical stimulation of structures in the operative field and the evaluation of the compound muscle action potentials recorded from the corresponding muscles of the head. Nerve function is monitored continuously by recording the ongoing electromyographic activity in these same muscles. Broadcasting electromyographic responses through a loudspeaker gives the surgeon immediate feedback on the status of the motor nuclei being monitored. Advantages of this technique include 1) the positive, objective identification of the nuclei and fiber tracts; 2) the continuous feedback on the status of these structures; 3) a safe approach through the fourth ventricle to the lesions in the brain stem; 4) the positive identification of the boundaries between the neoplasm and the motor structures of the rhomboid fossa; and 5) a warning to the surgeon of potentially harmful nerve manipulations (contact, dissection, transection) during surgery. After this technique was used in 16 consecutive operations to remove cavernomas (n = 9), gliomas (n = 4), and other types of tumors (n = 3), surgical and neurological results showed the method to be reliable and simple to perform.

Surgery of astrocytomas in the motor and premotor cortex under local anesthesia: report of 11 cases.

Under local anesthesia, gliomas of the premotor and primary motor cortex can be surgically removed with minimal morbidity. However, since these neoplasms exhibit an infiltrative growth pattern towards the pyramidal tract and are frequently not well delineated from functional motor cortex, the long-term outcome is unfavorable. In this series, 5 of 11 patients presented with a recurrent tumor within two years of operation. Two of these patients with recurrent tumors initially had a low grade glioma and three an anaplastic glioma. Due to the longer progression-free interval after surgery and the unpredictable course of patients with low grade gliomas, all efforts should be undertaken to achieve safe and radical resection with the use of intraoperative mapping and monitoring techniques as well as cryo-cut examinations at all tumor border zones to prove radicality. Since malignant tumors are known to recur in most instances, radical resection is justified only in functionally safe areas.

Severe symptomatic vasospasm after rupture of an arteriovenous malformation.

A 31-year-old woman had intracerebral and intraventricular hemorrhage from an arteriovenous malformation. Vasospasm of the internal carotid arteries developed and was treated with angioplasty. On initial CT scans, only traces of blood were seen in the basal cisterns; thus, the development of symptomatic vasospasm was an unexpected complication.

Circumscribed low grade astrocytomas in the dominant opercular and insular region: a pilot study.

Intraoperative mapping techniques allow a reliable identification or exclusion of eloquent brain areas and are well tolerated by the patients. In dominant opercular tumours radical surgery can only be achieved without lasting deficits with intraoperative histological examination of the resection line and mapping. If an early postoperative MRI shows residual opercular tumour in non-eloquent areas re-operation is recommended. In large dominant insular or opercular-insular tumours only biopsy is recommended, because only an incomplete removal can be accomplished, because the trial of radical removal carries a high risk of postoperative deficits due to possible vascular damage of the lenticulo-striate arteries or internal capsule. Because subtotal removal of low grade gliomas does not increase the progression free interval, we would not recommend surgery in these cases, as they carry a significant risk of a further deficit.

Transcranial color-coded duplex sonography in cerebral aneurysms.

BACKGROUND AND PURPOSE: Diagnosis and successful therapy before rupture of cerebral aneurysms would be most desirable in view of the high mortality and morbidity rates of aneurysmal subarachnoid hemorrhage. Using transcranial color-coded duplex sonography, we studied radiologically proven cerebral aneurysms to define ultrasonographic criteria and sensitivity for their diagnosis and detection. METHODS: Twenty-nine consecutive patients with 30 radiologically proven cerebral aneurysms were prospectively examined using transcranial color-coded duplex sonography. The sonographer was aware of cerebral computed tomographic and magnetic resonance imaging findings but was blinded to the results of cerebral angiography. RESULTS: Ultrasonographic findings for aneurysms studied were as follows: (1) Scanning planes that transsected approximately mid-aneurysm showed a round or oval mass that was divided by a "separation zone" into red and blue areas. (2) The "separation zone" was characterized by dark or no colors. (3) Peripheral scanning planes showed monochromatic images. (4) No turbulence was found. (5) No spontaneous fluctuations were detected. Twenty-three of 27 (85%) nonthrombosed aneurysms with a diameter of 6 to 25 mm were identified. The walls and three thrombosed and four nonthrombosed aneurysms (mean diameter, 5 mm) were missed. CONCLUSIONS: Transcranial color-coded duplex sonography can provide the diagnosis of nonthrombosed aneurysm using the above-cited criteria because of its capacity to reveal flow phenomena. It is not the method of choice in the search for aneurysms because small and thrombosed aneurysms are missed. Careful visual inspection of the intracranial arteries to permit incidental detection of cerebral aneurysms should be part of every transcranial color-coded duplex examination.