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.

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.

The importance of brainstem mapping in brainstem surgical anatomy before the fourth ventricle and implication for intraoperative neurophysiological mapping.

Brain stem mapping (BSM) is an intraoperative neurophysiological procedure to localize cranial motor nuclei on the floor of the fourth ventricle. BSM enables neurosurgeon to understand functional anatomy on the distorted floor of the fourth ventricle, thus, it is emerging as an indispensable tool for challenging brain stem surgery. The authors described the detail of BSM with the special emphasis on its clinical application for the brain stem lesion. Surgical implications based on the result of brains stem mapping would be also informative before planning a brain stem surgery through the floor of fourth ventricle. Despite the recent advancement of MRI to depict the lesion in the brain stem, BSM remains as the only way to provide surgical anatomy in the operative field. BSM could guide a neurosurgeon to the inside of brain stem while preventing direct damage to the cranial motor nuclei on the floor of the fourth ventricle. It is expected that understanding its advantage and limitations would help neurosurgeon to perform safer surgery to the brain stem lesion.

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.

Surgical strategy and outcomes for epileptic patients with focal cortical dysplasia or dysembryoplastic neuroepithelial tumor.

PURPOSE: The purpose of this study was to clarify and compare the influence of surgical strategy on relief from seizures in patients with focal cortical dysplasia (FCD) and those with dysembryoplastic neuroepithelial tumor (DNT). METHODS: Six patients with FCD and five patients with DNT, all of whom underwent surgical resection for medically intractable epilepsy, were compared in terms of presurgical seizure types and frequency, location of lesions, magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) with 99mTc-ECD, scalp electroencephalogram (EEG), and long-term video-EEG recording. Prolonged subdural recordings and intraoperative electrocorticograms (ECoG) were analyzed. The influences of surgical strategies on seizure outcomes were retrospectively analyzed. RESULTS: In all the FCD patients, ictal SPECT revealed hyperperfusion in the regions where MRI showed FCD. Interictal epileptiform activity and ictal seizure onset on ECoG performed with subdural electrodes were localized on the FCD itself. In contrast, the tumors of all the DNT patients were depicted as hypoperfuse areas on interictal SPECT scans. Ictal SPECT in one DNT patient showed hyperperfusion in the area enclosing the tumor. Interictal spiking in all DNT patients and ictal seizure onset in two DNT patients were not in the lesions themselves but in an area enclosing the lesion. All but one patient with FCD who underwent total lesionectomy became seizure free. All DNT patients who underwent resection of the epileptogenic cortex associated with lesionectomy became seizure free or achieved a 90% reduction in seizures. CONCLUSIONS: FCD has intrinsic epileptogenicity, whereas DNT is encompassed by epileptogenic cortical areas. Therefore, total lesionectomy is an essential strategy for FCD, whereas resection of the epileptic focus associated with lesionectomy of a DNT lesion is necessary to control seizures.

Intramedullar stimulation of the facial and hypoglossal nerves: estimation of the stimulated site.

AIM: To determine the stimulation site of both facial and hypoglossal nerves after transcranial magnetic stimulation. METHODS: After surgical exposure of the brainstem in 22 patients with intrinsic pontine (n=9) or medullary (n=13) tumors, the facial colliculus and the hypoglossal triangle were electrically stimulated. The EMG responses were recorded with flexible wire electrodes from the orbicularis oculi/orbicularis oris muscles, and genioglossal muscles. Patients had no preoperative deficit of the nerves. RESULTS: The EMG mean latencies of the unaffected facial nerve were 5.2+/-0.6 ms for the orbicularis oculi, and 5.2+/-0.5 ms for the orbicularis oris muscle. After the stimulation of 18 possibly affected facial nerves, the EMG mean latencies were 5.3+/-0.3 ms for the orbicularis oculi (p=0.539, unpaired Student's t-test), and 5.4+/-0.2 ms for the orbicularis oris (p=0.122). The EMG mean latency of the unaffected hypoglossal nerve was 4.1+/-0.6 ms for the genioglossal muscle. After the stimulation of 26 possibly affected hypoglossal nerves, the EMG mean latency for the genioglossal muscle was 5.3+/-0.3 ms. There was a significant difference (p<0.001) in latency for genioglossal EMG responses between the patients with pontine and those with medullary tumors. CONCLUSION: Shorter EMG mean latencies of unaffected facial nerves obtained after direct stimulation of the facial colliculi confirm that magnetic stimulation is most likely to occur closer to the nerve's exit from the brainstem than to its entrance into the internal auditory meatus. The hypoglossal nerve seems to have the site of excitation at the axon hillock of the hypoglossal motor neurons.

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.

Anatomical variants in the floor of the third ventricle; implications for endoscopic third ventriculostomy.

Longstanding hydrocephalus and raised intracranial pressure can lead to unusual anatomical variants in the floor of the third ventricle, which may be important when performing endoscopic third ventriculostomy. Two middle aged patients with symptomatic longstanding hydrocephalus had scans that showed ventricular hydrocephalus, an empty sella, and a dilated infundibular recess which herniated into the sella turcica. Endoscopic third ventriculostomy confirmed that instead of the tuber cinerum and infundibular recess, the anterior inferior floor of the third ventricle was hanging down ventral to the pons into the sellar floor. Third ventriculostomy to the prepontine cistern was made on the dorsal wall of the dilated infundibular recess to the area surrounded by the dorsum sellae, the basilar artery trunk, and the left superior cerebellar artery, with good symptomatic control. Association of the empty sella and persistence of the infundibular recess must be carefully evaluated by MRI before attempting endoscopic third ventriculostomy. Herniation of the anterior inferior floor of the third ventricle into the empty sella can lead to loss of anatomical landmarks that require special attention during third ventriculostomy.

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.

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 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.

Preserved motor evoked potentials fail to predict functional outcome in quadriplegia because of bilateral lesions of the supplementary motor areas: a brief report.

We present a patient with a lesion of the mesial frontal cortex, including the supplementary motor areas bilaterally, who on clinical examination revealed no spontaneous movements, although neurophysiological examination indicated integrity of the corticospinal tract to thenar and tibialis anterior muscles bilaterally. The patient was alert, speech was hesitant, and he was able to move his hands only on command. The role of the supplementary motor areas in planning, setting, and execution of skillful voluntary movements has been previously established by direct cortical electrical stimulation and studies of regional cerebral blood flow. The findings in our patient support the role of the supplementary motor areas in initiating movements. The presence of motor evoked potentials after acute insults to the brain is considered to be associated with a good functional outcome. This is in contrast to our patient who did not show improvement in motor performance, despite preserved motor evoked potentials. Hence, in the case of bilateral lesions to the supplementary motor areas sparing the corticospinal tract, the presence of motor evoked potentials may not predict functional recovery.

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.

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 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.

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.

Introduction of a second working portal for neuroendoscopy. A technical note.

The introduction of a second portal during endoscopic procedures in presented. This second portal allows passage of larger instruments while the surgical field is viewed with an endoscope placed through the first portal. This dual portal technique provides an angled view of the operative site, thus avoiding optical obstruction by tissue being pulled toward the endoscope. We report the use of this technique in 6 endoscopic cases.

Motor evoked potentials during brain surgery.

In order to obtain a robust method for intraoperative monitoring of motor pathways, different stimulation patterns to elicit muscle motor evoked potentials (MEPs) were studied during neurosurgical procedures in 3 patients. MEPs were recorded by a catheter electrode in the subdural space and/or by needle electrodes in limb muscles. For stimulation single pulses and trains consisting of two to five pulses were used. Muscle MEPs were only obtained after trains of at least 3 stimuli while single/double stimuli were inefficient. Simultaneous subdural recordings showed that single and double stimuli only elicited D-waves, whereas trains of 3 or more stimuli generated I-waves, as well. We propose that train stimulation can overcome the depressive effects of anesthesia on cortical motoneurons.