Ventral anchoring of the conus medullaris: a new surgical technique preventing the radiographic recurrence of retethering after surgery for tethered spinal cord.

OBJECTIVE: Retethering is not an unusual operation for a congenital lumbosacral dysraphic spinal lesion. The present study aimed to assess a new surgical technique for preventing retethering. SURGICAL TECHNIQUE: After untethering the spinal cord, the pia mater or scar tissue at the caudal end of the conus medullaris is anchored to the ventral dura mater loosely using 8-0 thread, and the dura mater is closed directly. This technique is called ventral anchoring. RESULTS: Ventral anchoring was performed in 15 patients (aged 5 to 37 years old, average age: 12.1 years old) between 2014 and 2021. All but one patient showed improvement or stabilization of the preoperative symptoms. No complication directly related to the procedure was observed. Postoperative MRI demonstrated that the dorsal subarachnoid space was restored in 14 patients but was undetectable or absent in three patients on follow-up MRI. No patients have experienced a recurrence of the tethered cord syndrome during the follow-up period. CONCLUSION: Ventral anchoring is effective for restoring the dorsal subarachnoid space after untethering the spinal cord. This preliminary study suggested that ventral anchoring has the potential to prevent the postoperative radiographic recurrence of tethered spinal cord in patients with a congenital lumbosacral dysraphic spinal lesion.

Vascular compression of the medulla oblongata by the vertebral artery: report of two cases.

OBJECTIVE AND IMPORTANCE: Compression of the medulla oblongata by a tortuous vertebral artery is rare. We report two patients with this lesion who were treated with vascular decompression of the vertebral artery. CLINICAL PRESENTATION: A 36-year-old man developed right hemiparesis with lower cranial nerve deficits, and a 47-year-old man developed left lower cranial nerve deficits and left cerebellar dysfunction. In both patients, magnetic resonance imaging revealed a tortuous vertebral artery compressing the medulla oblongata. INTERVENTION: In both patients, the compressed medulla oblongata was treated by detaching the vertebral artery from the medulla oblongata, shifting it, and anchoring it to the nearby dura mater. Postoperatively, both patients are asymptomatic and have returned to their previous jobs. CONCLUSION: Although compression of the medulla oblongata by a tortuous vertebral artery is rare, it can cause brainstem dysfunction. Magnetic resonance imaging clearly revealed the vascular compression in these patients. Surgical treatment was effective. The symptoms related to a tortuous vertebral artery and some techniques for surgical treatment are discussed. Awareness of this rare lesion is necessary to ensure appropriate treatment.

Functional anatomic relationship between brain-stem tumors and cranial motor nuclei.

OBJECTIVE: To identify patterns of cranial motor nuclei (CMN) displacement in cases of intramedullary brain stem tumor, using neurophysiological mapping of motor nuclei on the floor of the fourth ventricle. METHODS: Relationships between tumors and CMN were reviewed in 18 patients with brain stem tumors (seven pontine, nine medullary, and two pontomedullary tumors) and 2 with cervicomedullary junction spinal cord tumors. CMN VII, IX/X, and XII were mapped by applying electrical stimuli over the surgically exposed fourth ventricular floor through a handheld probe and recording electrical activity in the appropriate cranial muscles. RESULTS: Tumors distorted the anatomic location of CMN in repetitive patterns according to tumor site. Three patterns were identified as follows: Type 1, CMN located around the tumor on the floor of fourth ventricle; Type 2, one or more CMN located ventrally to the tumor; Type 3, CMN in original anatomic position. Six of seven patients with pontine tumors showed the Type 1 pattern. Seven of nine patients with medullary tumors showed Type 2, and the other two showed Type 1. Both patients with pontomedullary tumors showed Type 2. One patient with a cervicomedullary junction spinal cord tumor showed Type 1 and the other Type 3, depending on the tumor extension into the fourth ventricle. CONCLUSION: Pontine tumors push the CMN to around the tumor edge, suggesting that precise localization of CMN before tumor resection is necessary to avoid their damage. Medullary tumors grow more exophytically and compress the CMN ventrally. Understanding patterns of CMN displacement can help surgeons establish the surgical plan, minimize risks, and enable safer surgery of brain stem tumors.

Brain stem mapping: neurophysiological localization of motor nuclei on the floor of the fourth ventricle.

We have improved upon a brain stem mapping technique that can be used to locate cranial motor nuclei on the floor of the fourth ventricle. This technique helped to intraoperatively locate the facial colliculus and the motor nuclei of cranial nerves IX/X and XII in 14 patients undergoing removal of brain stem tumors. The motor nuclei of these cranial nerves are usually located relative to specific anatomic landmarks on the ventricular floor. These landmarks were not evident in most patients studied because of the distorting effects of the tumor. Different points of the floor of the fourth ventricle were electrically stimulated while electromyographic responses were recorded with electrodes inserted in the orbicularis oculi and orbicularis oris muscles, the lateral posterior pharyngeal wall, and the intrinsic muscles of tongue. Mapping was performed before and after tumor resection. The technique was found to be useful for locating cranial motor nuclei before tumor resection. It enabled surgeons to avoid damaging the nuclei when entering the brain stem. This technique, however, has certain limitations. Because this is a mapping technique, not a monitoring technique, continuous monitoring during tumor resection was unavailable. Also, the presence of a muscle response after tumor resection did not always indicate preservation of immediate postoperative function (7 days after surgery) because damage to the corticobulbar tract and/or the underlying neural circuitry was not detectable by mapping. Further research is needed to determine the point of stimulation in the functional motor circuitry and the relationship between intraoperative recordings and postoperative function in the long term.

Giant aneurysms of the horizontal segment of the anterior cerebral artery: report of two cases.

Two cases of giant aneurysm of the horizontal segment of the anterior cerebral artery (A1) are presented. The rare occurrence of a giant aneurysm in this location necessitates evaluation of the cross-flow through the anterior communicating artery when planning surgical strategy. On the basis of angiographic findings, trapping of the A1 on both sides of the aneurysm neck was performed in Case 1, and aneurysmorrhaphy utilizing an angioplastic multiple-clipping method of A1 endarterectomy was accomplished in Case 2. The postoperative courses of both patients were satisfactory.

The role of motor evoked potentials during surgery for intramedullary spinal cord tumors.

OBJECTIVE: This is a prospective study of the methodology and clinical applications of motor evoked potentials (MEPs) during surgery for intramedullary spinal cord tumors. METHODS: Transcranial electrical stimulation was used to activate corticospinal motoneurons, and the traveling waves of the spinal cord were recorded through catheter-electrodes placed epi- or subdurally. Intraoperative MEP monitoring was performed in 32 consecutive patients (age range, 1-50 yr) undergoing resection of intramedullary spinal cord tumors. In 19 patients, MEPs were present before myelotomy (monitorable group), and in 10 patients, MEPs were absent before myelotomy (unmonitorable group). Placement of an epidural electrode was not possible in two patients, and technical problems prevented recording in one. RESULTS: MEP amplitudes decreased intraoperatively by more than 50% of baseline in three patients, all of whom had postoperative paraplegia. Two of these patients recovered within 1 week after surgery, and one remained paraplegic. None of the patients with preserved MEP amplitude (> 50%) sustained immediate significant postoperative deterioration. Motor function was significantly deteriorated 1 week after surgery in one patient in the monitorable group and in five patients in the unmonitorable group. MEP monitorability was significantly associated with good surgical outcome for adult patients (P < 0.05), although not for pediatric patients (P > 0.6). Preoperative motor status and surgical outcome were not significantly associated for the adult (P = 0.13) or pediatric groups (P > 0.4). CONCLUSION: MEP monitorability was a better predictor of functional outcome than the patient's preoperative motor status for the adult group. Significant predictors of MEP monitorability in the adult group were preoperative motor function (P < 0.01), history of no previous treatment (surgery or irradiation) (P < 0.01), and small tumor size (P < 0.05). Weak associations with monitorable MEPs existed for low-grade tumors (P = 0.09), the presence of baseline somatosensory evoked potentials (P = 0.10), and tumor pathological abnormalities (ependymoma) (P = 0.13). No associations were determined for sex (P > 0.4), associated syrinx (P > 0.3), or tumor location (P > 0.5). In the pediatric group, none of the examined factors were associated with MEP monitorability (P > 0.3). A decline of more than 50% in MEP amplitude during tumor removal should serve as a serious warning sign to the surgeon.

Spinal cord and nerve root monitoring in spine surgery and related procedures.

Intensive research in the field of intraoperative neurophysiologic monitoring has been performed directed at finding reliable stimulating and recording techniques and adequate anesthetic regimes applicable to spinal procedures. The aim is a comprehensive monitoring not only of afferent and efferent spinal cord pathways but also of sensory and motor nerve roots and cauda equina fibers. Conventional somatosensory evoked potentials (SEPs) are complemented by motor evoked potentials, dermatomal sensory evoked potentials, spinal cord evoked potentials, evoked electromyography, sensory and motor fiber mapping of the cauda equina, bulbocavernosus reflex testing, and neurogenic evoked potentials. Apart from describing the essentials of these techniques and their indications and limitations, this article deals with the influence of anesthetic management on the production and interpretation of evoked potentials.

Magnetic resonance imaging of human spinal cord infarction.

Magnetic resonance images obtained in two cases of spinal cord infarction are described: one with hemorrhagic thoracic cord infarct, the other with ischemic cervical cord infarct with sequential magnetic resonance imagings. An enlarged cord with strand-shape or longitudinal hypointensity on both T1- and T2-weighted images was noticed in the hemorrhagic infarct; hypointensity on the T2-weighted image was thought to be due to hemosiderin, which shortens T2 relaxation. In the ischemic infarct, a small, round area of hypointensity on T1-weighted images, and of hyperintensity on T2-weighted images, noted 9 hours postictus ("early infarct") changed on the 22nd day to a cephalocaudal strandlike hypointensity on T1-weighted image, which was enhanced by Gd-DTPA. The hypointensity suggested "pencil-like softening" in "medium" age infarct. On postictal day 49, it showed an extensive homogeneous hypointensity involving several segments of the cord on T1-weighted images and hyperintensity on T2-weighted images with negative Gd-DTPA enhancement suggesting "late transverse infarct." We considered that these changes are of value in diagnosing spinal cord infarcts on magnetic resonance imagings.

Obstructive hydrocephalus due to a giant aneurysm of the internal carotid bifurcation.

A rare case of obstructive hydrocephalus associated with a giant aneurysm of the internal carotid artery is presented. The giant aneurysm, which was located in the prepontine cistern, was initially thought to be of basilar artery origin. Cerebral computed angiotomography had the most diagnostic value in disclosing the partially thrombosed giant aneurysm and its relationship with the surrounding arteries. After undergoing a ventriculoperitoneal shunt operation, the patient's clinical symptoms markedly improved.

Intraspinal sarcoidosis: diagnosis and management.

OBJECTIVE: Isolated intramedullary spinal cord or cauda equina involvement by sarcoidosis is quite rare. We report three patients with intraspinal sarcoidosis and absent systemic manifestations of the disease. The clinical presentation, operative management, electrophysiologic studies, pathology, laboratory investigations, and current therapy are discussed with attention to the previous literature. METHODS: Two of the three patients had a preoperative diagnosis of a cervical intramedullary spinal cord tumor. The third patient had the preoperative diagnosis of an infectious process involving the cauda equina. Magnetic resonance imaging (MRI) with gadolinium did not suggest an inflammatory process. Intraoperative somatosensory evoked potential performed in two patients exhibited normal amplitudes, but a prolonged latency in seven out of eight extremities; with normal central conduction time suggesting a peripheral or radicular involvement. All three patients underwent laminectomy and biopsy of the intraspinal pathology. RESULTS: Pathologic examination demonstrated sarcoidosis in all three patients. Intraoperative observations, intramedullary nodules, and thickening of the meninges were inconsistent with neoplasm and limited the surgical procedure to a biopsy. Frozen sections performed at two of the operations revealed an inflammatory process that confirmed the intraoperative observations. Postoperatively, the diagnostic work-up for all patients was negative for systemic manifestations. CONCLUSIONS: Isolated intraspinal sarcoidosis is a rare process. The current management for intramedullary spinal cord or cauda equina sarcoidosis is prolonged corticosteroids. The surgeon should not attempt complete resection if this granulomatous process is suspected.

Functional posterior rhizotomy for severely disabled children with mixed type cerebral palsy.

The authors evaluated the impact of functional posterior rhizotomy (FPR) for children with severely disabled mixed type cerebral palsy (CP). Three quadriplegic children at the age of 3, 4, and 10 years underwent FPR. They were classified as mixed type CP based on the clinical presentation of marked spasticity with dystonic posture. Preoperative Ashworth score of the lower extremity was 3.5, 4.5, 4.8 respectively. Two children showed prominent opisthotonus and all showed severe subluxation of the hip joint. Advanced scoliosis was associated in two children. FPR was performed from L2 to S1 in one child, L2 to S2 in one and L2 to S1/S2 in one based on the result of pudendal mapping. Rootlet cutting rate ranged from 66 to 75%. Postoperatively, Ashworth score dropped to 1.4, 1.2, 1.3, respectively. Functional improvement of the upper extremity and urination were confirmed in two children. Hip subluxation was reduced in one child and remained stable in two. A one-year follow-up review confirmed no relapse of spasticity among them. FPR achieved highly satisfactory surgical effects in children with severe mixed type CP. Although long-term follow-up is mandatory since there was a report of relapsed spasticity after FPR in this particular population of CP, FPR could be a choice of surgery in severely disabled children with mixed type CP.

Giant basilar bifurcation aneurysm presenting as a third ventricular mass with unilateral obstructive hydrocephalus: case report.

We report a rare case of a non-ruptured basilar bifurcation aneurysm presenting as a third ventricular mass producing unilateral obstructive hydrocephalus. This is the first reported case of its kind. A 70 year old woman presented with a giant basilar bifurcation aneurysm in which the aneurysm protruded into the third ventricle as a mass causing unilateral left hydrocephalus. The patient gradually became disoriented and developed a right hemiparesis and global aphasia. The right vertebral artery was occluded by placing coils intravascularly followed by an endoscopic septostomy. The patient's neurological state dramatically improved immediately. One month after the septostomy, however, the aneurysm ruptured and the patient eventually died. Treatment of the hydrocephalus only was selected instead of direct surgery or an intravascular procedure on the aneurysm, which eventually ruptured. The mechanisms for the unilateral hydrocephalus and the rupture of the aneurysm are described. The treatment strategy for these lesions is also discussed.

Non-ruptured large dorsal internal carotid artery aneurysm presenting with temporal quadrantanopsia.

A 63-year-old woman presenting with temporal lower quadrantanopsia of the right eye was found to have a large dorsal internal carotid artery aneurysm. Large dorsal aneurysms of the internal carotid artery are rare. Lateral compression of the optic nerve by the aneurysm might damage the optic nerve at the medial side of the right optic foramen. Direct clipping surgery was performed uneventfully. Since the dome of the aneurysm was buried in the frontal lobe and also attached to the anterior skull base, a careful approach to the aneurysm with removal of the anterior clinoid process and drilling into the planum sphenoidale around the aneurysm dome was needed. The surgical strategy is discussed.

Surgical resection of cerebral arteriovenous malformation combined with pre-operative embolisation.

To assess the importance of pre-operative embolisation, 27 cases of cerebral artriovenous malformation (AVM) treated in this institute between July 1994 and October 1998 were analysed. The patients' ages ranged from 3 to 70 years (average 36.9) with a follow-up period of 1-41 months (average 19.2). The patient presented with haemorrhage in 21 cases and seizure in five. In 21 of 27 cases, surgical resection of a nidus was performed, gamma knife therapy was applied in three and conservative therapy was chosen in three. Of 21 cases treated surgically, total removal was achieved in 19 cases and a residual nidus was seen in one (a large basal ganglia AVM). In the remaining case, postoperative angiography was not available. Pre-operative embolisation followed by surgical resection of the nidus was performed in seven cases in which there was a large AVM. A volume index was calculated to indicate the size of the nidus using X x Y x Z, where X is the maximum diameter (cm) of the nidus on the lateral angiogram, Y is the diameter (cm) perpendicular to X and Z is the maximum diameter (cm) on the anteroposter or angiogram. The index averaged 45.9 for the cases in which pre-operative embolisation was performed, while it was 5.6 in the cases without embolisation. Pre-operative embolisation was performed to reduce the nidus flow as much as possible, to prevent overload to the surrounding structures. At surgery, the nidus was resected from the surrounding tissue and care was taken not to enter the nidus. Postoperatively, the systolic blood pressure was maintained at 90-100 mmHg for several days in the intensive care unit. The results were excellent in 15 cases, good in three (hemiparesis due to the initial haemorrhage remained in all three), fair in one (a patient with a severe subarachnoid haemorrhage). Two patients died (acute pulmonary oedema and severe meningitis). Minor postoperative bleeding or oozing was seen in three cases. In conclusion, reducing the shunt flow through a nidus in a step-wise fashion with pre-operative embolisation of a large AVM seems to be quite helpful in preventing postoperative haemodynamic overload to the surrounding brain. It is also important not to enter the nidus when it is removed at surgery. This helps to prevent intraoperative and/or postoperative bleeding, and led to successful total removal of the nidus with a good postoperative course.

Revascularization of the calcarine artery in moyamoya disease: OA-cortical PCA anastomosis--case report.

A 38-year-old male presented with moyamoya disease. Occlusion of the bilateral proximal posterior cerebral arteries (PCAs) resulted in homonymous 3/4 (right half and left lower quadrant) anopsia and various mental symptoms. To prevent impending cortical blindness, revascularization to the right PCA was performed by occipital artery (OA) to calcarine artery anastomosis. His neurological state was stabilized. OA-cortical PCA (calcarine artery) anastomosis is an alternative to omentum transplantation or occipital burr hole procedures for impending cortical blindness.

Electrodiagnosis in the management of brachial plexus surgery.

A few pre and intraoperative neurophysiological tests offer valuable information in the diagnosis and functional evaluation of brachial plexus injury. The tests and the questions they answer can guide the surgeon's decision about whether to perform neurolysis or an interpositional graft.

[The experiences of a large amount of steroid therapy for symptomatic vasospasm after subarachnoid hemorrhage: clinical analysis of 21 cases].

Among 48 cases of subarachnoid hemorrhage, 21 cases (43.8%) showed symptomatic vasospasm. We attempted treatment, using a large amount of steroid therapy for them in accord with our own protocol. In the 21 cases who received steroid therapy for symptomatic vasospasm, 18 cases (85.7%) showed improvement of their symptoms. This was especially evident in about 8 cases where the steroid effect was remarkable. There was a serious side effect, GI--tract bleeding, in one case. Although the effect of the steroid therapy was evident for slight or moderate spasm cases, 5 severe spasm cases responded poorly. We concluded that a large amount of steroid therapy was effective for slight or moderate symptomatic vasospasm cases, and that in severe ones possibly another therapy combined with steroid therapy would be necessary.

[Computerized tomography immediately after surgery in the neurosurgical operating theater].

A TCT-300 scanner (manufactured by the Toshiba Co., Tokyo) has been installed in the operating room of Shinshu University Hospital since 1986. This neurosurgical operating CT scanner system was developed for obtaining intra- and postoperative CT images in the operating room. We have carried out immediate postoperative CT scanning in 206 cases: 170 were major and 36 were minor operations. A mobile CT scanner gantry has been used in 125 cases since June, 1988. We obtained CT images immediately after surgery on the digitalized operating table, the motion of which can be controlled as with the conventional CT scanner table. Immediate postoperative CT scans showed the extent of removed tumors or hematomas, position of the tip of ventricular or cisternal tubes, injury to the surrounding normal brain caused during the removal of lesions, and postoperative complications such as hemorrhage, brain swelling and surgical patties which had been inadvertently left in the wound. This CT scanner system in the operating room proved to be useful in the postoperative care of neurosurgical patients.

[Functional posterior rhizotomy as a surgical treatment for spastic cerebral palsy in childhood].

The author reported a case of spastic cerebral palsy in a 4-year-old boy who underwent functional posterior rhizotomy and were followed up for more than one and a half years after surgery to evaluate the degree of spasticity. The patient's preoperative ADL was highly restricted due to severe spasticity. In the surgery, the bilateral rootlets from L2 to S1 were selectively cut if an abnormal reflex activity was demonstrated by neurophysiological methods. Spasticity markedly decreased postoperatively and alleviated the family's burden for daily care. During the period of follow up, residual spasticity has subsided and the effect in controlling spasticity was long-standing. Functional posterior rhizotomy has been recognized as an established neurosurgical treatment for spastic cerebral palsy in childhood in the North America. However, the procedure is uncommon in Japan. The author outlined here the procedure and its history. Functional posterior rhizotomy is a strong armament for treating spasticity in cerebral palsy. The procedure would greatly benefit patients with spastic cerebral palsy in combination with current treatments.

High-flow Neonatal Macrocerebral Arteriovenous Fistulas in Hereditary Hemorrhagic Telangiectasia.

Although some cases of vein of Galen aneurysmal malformation (VGAM) present initial clinical symptoms such as cardiopulmonary disturbance in the neonatal period, pial arteriovenous fistula is very seldom present as a clinical symptom immediately after birth. A neonatal patient, the first-born to his family, presented with tachypnea postpartum. This baby had a family history of hereditary hemorrhagic telangiectasia. A cerebral MR image revealed multiple macrocerebral arteriovenous fistulas (MCAVFs), resulting in a large partially thrombosed venous pouch within the cerebral cortex. Trans-arterial embolizations of the main two fistulas were performed using N-butyl cyanoacrylate (NBCA) with tantalum powder six months after birth. Post-embolization angiography confirmed the obliteration of the fistulas and magnetic resonance imaging (MRI) revealed thrombosis and reduction in size of the venous component. His tachypnea disappeared completely. There were no neurological complications due to the treatment. The prognosis of multiple MCAVFs mainly depends on the presence of medullar signs and symptoms and a delay before treatment. Pure glue endovascular intervention, as used in our case, is considered to be the first therapeutic choice to decrease the risk of neurological consequences.