A hypothesis of epiarachnoidal growth of vestibular schwannoma at the cerebello-pontine angle: surgical importance.

AIMS: The purpose of this study is to clarify the rearrangement of the arachnoid membrane on the vestibular schwannoma during its growth in relation to adjacent neurovascular structures for a better understanding of dissecting plane of arachnoid during surgery. METHODS: Arachnoid membrane over the tumour was investigated during surgery with suboccipital transmeatal approach in twenty-six tumours. All microsurgical procedures were recorded with a video and reviewed. The tumour growth was classified into five stages depending upon the tumour diameter in the cerebello-pontine (CP) angle: Stage 1; purely intracanalicular (2 cases), Stage 2; less than 5 mm (2 cases), Stage 3; > or = 5 and <15 mm (8 cases), Stage 4; > or = 15 and <25 mm (9 cases) and Stage 5; > or = 25 mm (5 cases). Rearrangement of the arachnoid on the tumour was conceptualised throughout all stages. RESULTS: All tumours of Stage 1 and 2 were entirely located in the subarachnoid space of the cerebello-pontine cistern without arachnoidal rearrangement, while all tumours of Stages 3 to 5 were enveloped, in the CP angle, with invaginated arachnoid membrane consisting of cerebello-pontine cistern except two surfaces; the medial pole and the tumour surface under the facial and cochlear nerves near the porus. CONCLUSION: The tumour originates subarachnoidally within the internal auditory meatus (IAM) and grows epiarachnoidally in the CP angle. Rearrangement of the arachnoid begins with its adhesion on the medial pole of the tumour along the porus, resulting in the arachnoidal invagination into the cerebello-pontine cistern with further growing of the tumour.

Development of lumbosacral spina bifida: three-dimensional computer graphic study of human embryos at Carnegie stage twelve.

There is still some controversy as to whether sacral spina bifida in humans is the result of a defect of the primary or secondary neural tube. As somites are related to the development of vertebrae and the primary neural tube is related to the development of the spinal cord in embryos, it is very important to determine the number of somites in normal human embryos at the time of closure of the primary neural tube to understand the contribution of primary neural tube defects to the development of spina bifida. However, in the literature, the number of somites in stage 12 human embryos is still controversial. The aim of this study is to find the number of somites in human embryos at Carnegie stage 12. Four human embryos at Carnegie stage 12 were selected from the laboratory of the Congenital Anomaly Research Center in Japan. The neural tube and somites were reconstructed from their slices by a three-dimensional computer graphic reconstruction technique. The reconstructed embryos were examined from multidirectional magnified images. Thirty-three pairs of somites were present in all these reconstructed embryos. As the 33rd pair of somites corresponds to the fifth sacral segment, the presence of 33 pairs of somites at Carnegie stage 12 suggests that spina bifida develops from defects of the primary neural tube.

Syringomyelia associated with adhesive spinal arachnoiditis: MRI.

We reviewed the MRI of seven patients with syringomyelia associated with surgically proven adhesive spinal arachnoiditis to describe clinical and MRI findings in this condition. Using 0.5, 1.0 or 1.5 tesla units, we obtained sagittal T1- and T2-weighted spin-echo and axial T1-weighted images. Additional sagittal T2-weighted images were obtained without using motion-artefact suppression. Contrast medium was given intravenously to five patients. The syrinx cavities were thoracic in five cases, cervicothoracic in one, and extended from C4 to L1 in one. No Chiari malformation or craniovertebral junction anomaly was demonstrated. Meningeal thickening was seen on T2-weighted sagittal images only in one case. Cord deformity due to adhesion or displacement due to an associated arachnoid cyst was seen in all cases best demonstrated on axial images. Focal blurring of the syrinx wall on axial images was seen in six patients. Flow voids were seen in the syrinx fluid in all cases on T2-weighted images obtained without motion-artefact suppression. No abnormal contrast enhancement was demonstrated.

Surgical management of syringomyelia associated with spinal adhesive arachnoiditis.

The authors describe a new surgical technique to minimise the postoperative recurrence of adhesion after microlysis of adhesion to treat syringomyelia associated with spinal adhesive arachnoiditis. A 47 year old male presented with numbness of the lower extremities and urinary disturbance and was demonstrated to have a case of syringomyelia from C1 to T2 which was thought to be secondary to adhesive spinal arachnoiditis related to a history of tuberculous meningitis. Following meticulous microlysis of the adhesions, maximal expansion of a blocked subarachnoid space was performed by expansive duraplasty with a Gore-Tex surgical membrane, expansive laminoplasty and multiple tenting sutures of the Gore-Tex graft. Postoperatively, the syringomyelia had be en completely obliterated and improvement of the symptoms had been also achieved. The technique described may contribute to improvement of the surgical outcome following arachnoid dissection by maintaining continuity of the reconstructed subarachnoid space.

Suckling dysfunction caused by defects in the olfactory system in genetic arhinencephaly mice.

Mouse newborns find their mother's nipples and suckle milk by themselves. It has been argued which sense organ they use when locating their mother's nipples to suckle milk. Olfactory or tactile sensory systems are primary candidates. In the present study, we investigated the trigeminal-whisker sensory and olfactory systems in genetic arhinencephaly mouse embryos (Pdn/Pdn). Pdn/Pdn newborns do not suckle milk and die within 1 day after birth. Dysfunction of nipple-searching behavior was clear in Pdn/Pdn newborns. Pdn/Pdn newborns had a complete developmental failure in the olfactory nerve projection to the central nervous system and no olfactory bulb architecture. The trigeminal-whisker system was intact in this strain. From the results of these experiments, it was suggested that the olfactory system is essential for nipple-searching behavior and suckling milk and that the trigeminal-whisker system is not able to substitute for the lack of olfactory input in mouse newborns.

Contralateral approach to junctional C2-C3 and proximal C4 aneurysms of the internal carotid artery: microsurgical anatomic study.

OBJECTIVE: To evaluate a contralateral approach to aneurysms located in the internal carotid artery cave and proximal C4 segments. METHODS: In six adult cadaveric head sides, proposed aneurysms in the carotid cave or proximal C4 segments were approached via contralateral craniotomies. We summarize the approach in the following steps: 1) frontotemporal orbital craniotomy, 2) drilling of the lateral sphenoid wing and opening of the dura along the frontotemporal base, 3) drilling of the planum sphenoidale and the tuberculum sellae more extensively toward the aneurysm side and opening of the sphenoid sinus, 4) drilling of the medial part of the anterior clinoid process on the side of the aneurysm and removal of the superior, medial, and inferior walls of the optic canal, 5) opening of the optic sleeve, and 6) opening of the space between the medial wall of the internal carotid artery C2-C3 segments and the lateral edge of the pituitary gland. RESULTS: The contralateral approach to expose the opposite internal carotid artery cave and proximal C4 segments provided excellent views of the region, without mobilization or retraction of either the optic nerve or the carotid artery. CONCLUSION: We recommend that this approach be used only for selected aneurysms, which are small and directed medially, anteriorly, or inferiorly, in the defined locations.

Molecular cloning and characterization of a human homologue of TBPIP, a BRCA1 locus-related gene.

Here we clone the human homologue of TBPIP [Tat binding protein 1(TBP-1)-interacting protein]. TBPIP is a molecule that has been cloned from mouse as a cofactor of TBP-1. Eighty-eight per cent of the deduced amino acid sequence of human TBPIP coincides with that of mouse TBPIP. CAT assay reveals that human TBPIP could interact with human TBP-1, then enhance the function of TBP-1 on HIV (human immunodeficiency virus)-Tat-mediated transactivation. Our radiation hybrid mapping indicates that TBPIP is located on chromosome 17q12-21. A DNA database search uncovers that an apparent part of TBPIP has been obtained as a BRCA1 locus-related gene (OV-4) and mapped onto chromosome 17q12-21. Interestingly, the nucleotide structure of human TBPIP is very similar to that of the GT198 gene, which has been cloned from a human breast cancer cell line and also mapped onto the BRCA1 locus. Since a very high rate of gene mutation is observed in the BRCA1-related region in breast cancers and expression of authentic GT198 mRNA could not be confirmed in either BT-474 (other kind of human breast cancer cell line) or normal human testis (where the strong expression of GT198 mRNA is reported), it is likely that GT198 is a mutated form of human TBPIP.

Contralateral approach to carotid cave aneurysms.

BACKGROUND: To evaluate the surgical approach and clipping of aneurysms located at the carotid cave region. METHOD: Between 1980 and 1998 we have adopted the well known ipsilateral approach for exposure and securing of carotid cave aneurysms. In four patients, we had the opportunity to use a contralateral approach to carotid cave aneurysms, with easier dissection and application of a simple aneurysmal clip. The visual acuity of the patients did not deteriorate from the pre-operative level. FINDING AND INTERPRETATION: Aneurysms located at the carotid cave region may be approached easily and safely through a contralateral craniotomy with application of the aneurysm clip from an angle medial and inferior to the optic nerve.

Pathogenesis of encephaloschisis in retinoic-acid-treated hamster embryos I: a morphometric study of the craniofacial structures.

The severity of the developmental disorders of the paraxial mesoderm and neuroectoderm must objectively be compared to determine which of the two structures is more deeply involved in the pathogenesis of encephaloschisis. In the present study, hamster fetuses were obtained from dams that had been treated with retinoic acid, and divided into two groups: fetuses with encephaloschisis and those without apparent external malformations in the cranium and face. Mid-sagittal serial sections of the head were prepared, histologically processed, and utilized for the reconstruction of the profile of the head structures. Using this reconstructed profile, we measured the length of the skull base bone structures (basisphenoid and basiocciput), which develop from the paraxial mesoderm, brain structures (mesencephalon and metencephalon), which develop from the neuroectoderm, and facial bone structures (nasal septum and hard palate), which develop from cephalic neural crest cells. The measured length of each structure was compared between the treated and control groups. It was found that treatment with retinoic acid resulted in significantly (P < 0.05) shortened lengths of the skull base bone structures both in fetuses with encephaloschisis and those without apparent external malformations in the cranium and face. In the brain structure of fetuses without encephaloschisis, as well as in the facial bone structures, however, this shortness was not observed. These results suggest that developmental disorders in the paraxial mesoderm may play an important role in the pathogenesis of encephaloschisis.

Direct carotid-cavernous sinus fistula due to ruptured intracavernous aneurysm treated with electrodetachable coils--case report.

A 66-year-old female developed exophthalmos, impaired visual acuity (perception of light), and diplopia one day after sudden onset of headache. Neurological examination revealed proptosis, chemosis, impaired vision, and ophthalmoplegia. Carotid angiography showed direct carotid-cavernous sinus fistula concomitant with an intracavernous aneurysm on the right side. Intraaneurysmal embolization using the Guglielmi detachable coils (GDCs) via the transarterial route was performed and complete occlusion of the fistula successfully achieved. The neurological deficits resolved completely by 6 months after embolization. Intraaneurysmal GDC embolization via the transarterial route may be an alternative for the treatment of direct carotid-cavernous sinus fistula due to rupture of intracavernous aneurysm.

Expansive suboccipital cranioplasty for the treatment of syringomyelia associated with Chiari malformation.

In order to treat syringomyelia associated with adult type Chiari malformation, the authors developed a method of expansive suboccipital cranioplasty (ESC) that involves enlarging the small posterior fossa to obtain a sufficient flow of cerebrospinal fluid (CSF). The relative effectiveness of ESC with the obex plugged and not plugged was also examined, as well as other factors influencing the operative results. Twenty patients without arachnoid adhesion at the major cistern underwent ESC without opening the arachnoid membrane at the major cistern. After surgery, all improved with no recurrence and CSF flow study using magnetic resonance (MR) imaging showed significant improvement of the flow at the major cistern. Another 20 patients without arachnoid adhesion also underwent ESC but with obex plugging. Sixteen improved and one displayed only temporary improvement with recurrent syringomyelia due to postoperative arachnoid adhesions. The remaining three showed no change in spite of shrinkage of the syrinx on postoperative MR imaging. These three patients had displayed pre-operative symptoms over an approximately 10-year period involving almost the entire axial plain of the spinal cord, and presented a large syrinx before surgery. In 4 patients with arachnoid adhesions, all required intra-arachnoid procedures in addition to ESC. Intra-arachnoid procedures are not necessary to facilitate restoration of CSF flow in patients without arachnoid adhesions, because ESC can release the CSF flow blockage in the major cistern even without plugging of the obex. An associated arachnoid adhesion at the major cistern or a long-standing syringomyelia with irreversible damage of the spinal cord results in a poor operative prognosis. When posterior fossa surgery fails, insufficient decompression or postoperative arachnoid adhesions at the major cistern as the cause of treatment's failure should be evaluated by CSF flow studies using phase contrast MR imaging.

Posterior approach for cervical intramedullary arteriovenous malformation with diffuse-type nidus. Report of three cases.

The treatment of spinal intramedullary arteriovenous malformations (AVMs) with a diffuse-type nidus that contains a neural element poses different challenges compared with a glomus-type nidus. The surgical elimination of such lesions involves the risk of spinal cord ischemia that results from coagulation of the feeding artery that, at the same time, supplies cord parenchyma. However, based on evaluation of the risks involved in performing embolization, together with the frequent occurrence of reperfusion, which necessitates frequent reembolization, the authors consider surgery to be a one-stage solution to a disease that otherwise has a very poor prognosis. Magnetic resonance (MR) imaging revealed diffuse-type intramedullary AVMs in the cervical spinal cords of three patients who subsequently underwent surgery via the posterior approach. The AVM was supplied by the anterior spinal artery in one case and by both the anterior and posterior spinal arteries in the other two cases. In all three cases, a posterior median myelotomy was performed up to the vicinity of the anterior median fissure that divided the spinal cord together with the nidus, and the feeding artery was coagulated and severed at its origin from the anterior spinal artery. In the two cases in which the posterior spinal artery fed the AVM, the feeding artery was coagulated on the dorsal surface of the spinal cord. Neurological outcome improved in one patient and deteriorated slightly to mildly in the other two patients. Postoperative angiography demonstrated complete disappearance of the AVM in all cases. Because of the extremely poor prognosis of patients with spinal intramedullary AVMs, this surgical technique for the treatment of diffuse-type AVMs provides acceptable operative outcome. Surgical intervention should be considered when managing a patient with a diffuse-type intramedullary AVM in the cervical spinal cord.

Surgical outcome of intramedullary spinal cord ependymoma.

Surgical outcome of intramedullary spinal cord ependymoma was investigated in order to define the treatment strategy. We have operated on 18 cases of intramedullary spinal cord ependymoma based on the principle of radical resection. The follow-up periods ranged from 10 months to 249 months with an average of 86.2 months. Postoperative neurological status in the long follow-up periods was compared to the pre-operative status and was correlated with the histological grade of malignancy. Total removal of the tumour was achieved in 17 cases, and subtotal removal followed by radiation therapy was conducted in 1 case. There was neither surgical mortality nor radiological evidence of recurrence in the long-term follow-up periods. The final outcome of the neurological condition was improved in 1 case, unchanged in 15 cases (including a case of subtotal removal) and deteriorated in 2 cases. The deterioration was in the form of gait disturbance due to the worsening of proprioception in 2 cases and dysaethesia in 1 case. Histological examination showed no evidence of anaplasia in 6 cases, evidence of early anaplasia in 10 cases, and moderate evidence of anaplasia in 2 cases. No relationship between the histological malignancy and clinical course was found. Intramedullary spinal cord ependymoma should be removed radically as early as possible while taking great care to avoid posterior column injury. Histologically malignant ependymoma might be a clinical exception.

[A clinical study on long-term outcome in patients with syringomyelia associated with Chiari malformation].

To investigate the long-term outcome in patients with syringomyelia associated with Chiari malformation (chronic tonsilar herniation), we investigated the actual factors of the patient's problems by a questionnaire for the patient. Replies to the questionnaires were obtained from 44 patients with syringomyelia who had been treated with expansive suboccipital cranioplasty with dural plasty (with plugging of the central canal in 20 patients). In 25 cases (68%) in whom the motor dysfunction of the upper extremities remained, the symptoms improved in 16 cases (43%) and were unchanged in 9 cases (24%). In 18 cases (64%) in whom the motor dysfunction of the lower extremities remained, the symptoms improved in 10 cases (36%) and were unchanged in 8 cases (29%). In 31 cases (78%) in whom the sensory disturbance remained, the symptoms improved in 19 cases (48%) and were unchanged in 12 cases (30%). The motor dysfunction of the upper extremities persisted significantly in more patients having a duration of illness over 2 years than in patients with those less than 2 years. Sensory disturbance persisted significantly in more patients with a duration of illness over 3 years than in patients with that less than 3 years. These results suggest that firstly, sensory disturbance (disturbance of the posterior horn) is most apt to remain, then motor dysfunction of the upper extremities (disturbance of the anterior horn) and followed by motor dysfunction of the lower extremities (disturbance of the pyramidal tract). We conclude that patients should be treated before having irreversible spinal cord disturbance.

Efficacy of induced hypotension in the surgical treatment of large cavernous sinus cavernomas.

OBJECT: Cavernous sinus cavernomas are rare lesions associated with high rates of intraoperative mortality and morbidity resulting from profuse bleeding. In this paper, the authors report their experience in treating five patients with histologically confirmed cavernous sinus cavernomas and describe the efficacy of induced hypotension in facilitating excision of the lesion. METHODS: All five patients were women ranging in age from 25 to 54 years, with an average age of 42 years. The mass was small in one and large (>3 cm in diameter) in four. In one patient with a large mass, cardiac arrest occurred after the craniotomy, and remarkable reduction in the size of the cavernoma was evident on postmortem examination. The other three large lesions were successfully removed piecemeal after induction of hypotension (60-80 mm Hg systolic pressure), which remarkably reduced the mass and the bleeding during surgery. In the remaining patient, who had a small lesion, the cavernoma was removed in one piece. CONCLUSIONS: Cavernous sinus cavernoma can be thought of as a cluster of sinusoidal cavities, the size of which varies depending on the systemic blood pressure. During surgery, reduction of the mass and control of bleeding from the cavernoma can be achieved by inducing hypotension, which enables the safe excision of this lesion. This technique should be considered by surgeons resecting a cavernous sinus tumor, especially when cavernoma is suspected.

Determining the appropriate stimulus intensity for studying the dipole moment in somatosensory evoked fields: a preliminary study.

OBJECTIVE: To establish a simple method of determining the appropriate stimulus intensity for studying the dipole moment in somatosensory evoked fields. METHODS: In 17 patients (20 hemispheres), the authors studied the relationship between the dipole moment and stimulus intensity, which was quantified using the threshold of thenar muscle twitch (TMT). The dipole moment was measured at 1.0, 1.5 and 2.0 TMT. Two measurements were obtained at 1.5 TMT to determine the procedure's margin of error. RESULTS: There was no significant difference between the dipole moments measured at 1.5 and 2.0 TMT. CONCLUSIONS: Setting the stimulus intensity at 1.5 TMT or more ensures a consistent response.

Identifying mRNAs involved potentially in corticopontine projection by modified differential display.

The basilar pons plays an important role in the establishment of the corticopontine projection by releasing a diffusible molecule which induces and directs collateral branchings along the corticospinal axon shafts. To reveal the molecule which is involved in the developing process of the corticopontine projection, we attempted to modify the mRNA differential display to search for genes expressed differentially in the basilar pons during the formation of the corticopontine projection by introducing the RGD motif (arginine-glycine-asparate) in the primers of the polymerase chain reaction. With our modification, we were able to identify 99 mRNAs expressed in the basilar pons but not in the cerebral cortex where the apparent pontine-derived activity is not observed. Among these 99 gene fragments, 3 novel fragments could be selected as final candidates of the pontine-derived molecule based on their expression patterns. Modified differential display is thus a promising method for identification of these genes.

Aetiology of delayed facial palsy after vestibular schwannoma surgery: clinical data and hypothesis.

A patient developed delayed facial nerve palsy at the level of House-Brackmann grade I to grade III 10 days after vestibular schwannoma surgery by the suboccipital transmeatal approach. The palsy had completely recovered after one month. Immunological study showed reactivation of herpes simplex and magnetic resonance (MR) imaging demonstrated an abnormal enhancement pattern of the facial nerve; intense enhancement of the distal intracanalicular segment and labyrinthine segment, similar to the MR findings for Bell's palsy. A prospective control study on the enhancement pattern of the functionally preserved facial nerve after vestibular schwannoma surgery in six cases showed a similar pattern to that of the normal facial nerve. Based on these findings, we propose the hypothesis that herpes simplex reactivation is an underlying cause of delayed facial palsy after vestibular schwannoma surgery.

The effect of experimental spinal cord edema on the spinal evoked potential.

Experimental spinal cord edema was successfully produced in the cat intumescentia cervicalis by the infusion method of Marmarou. The water content around the infusion site significantly increased to 75.9% from the normal value of 69.8% of white matter in the lateral column, with the infusion of 20 microliters of autoserum. The edema was observed for a length of ca.20 mm, spreading mainly longitudinally in the lateral column. The spinal evoked potential was measured four times on the course of infusion and the N1 peak latency at the end of infusion did not show any significant difference compared to the value before infusion. This model may contribute to basic understanding of pathophysiology of spinal cord edema by changing the nature and the volume of infusate, and the location of infusion, according to the experimental purpose.

Occlusion of the sigmoid sinus after surgery via the presigmoidal-transpetrosal approach.

OBJECT: In this paper the authors report on sigmoid sinus occlusion as a surgical complication in seven of 143 operations in which a presigmoidal-transpetrosal approach was used. METHODS: Five patients (Cases 1-5) developed occlusion within 40 days after surgery, and in the remaining two (Cases 6 and 7) occlusion was detected 5.4 and 6.4 years postsurgery by means of cerebral venography, which was performed in 40 of the remaining 138 patients. Of the two patients with occlusion of the hypoplastic transverse sinus, one (Case 1) did not develop symptoms and the other (Case 2) developed brain edema with transient aphasia. Of the three patients suffering from occlusion of the dominant sigmoid sinus, one (Case 3) developed severe intracerebral hemorrhages and had a poor prognosis; one (Case 4) developed profuse supra- and infratentorial brain edema with consciousness disturbance; and the other (Case 5) developed hemorrhagic infarction in the temporal lobe accompanied by aphasia. Two patients whose sinus occlusion was detected later (Cases 6 and 7) did not develop symptoms and displayed well-communicated transverse sinuses. In Case 7, a dural arteriovenous malformation formed at the site of the sinus occlusion. Laceration of the sigmoid sinus was suspected as the cause of occlusion in Cases 2, 3, and 7; compression of the sinus in Cases 5 and 6, sinus laceration and postoperative dehydration in Case 4; and laceration and compression of the sinus in Case 1. CONCLUSIONS: Differences in the clinical course among these patients were attributed to anatomical variations in the venous system. Occlusion of the sigmoid sinus should be weighed as a potential complication when selecting candidates for the presigmoidal-transpetrosal approach.