Fred Epstein

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 patients 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.

Twenty-year experience with early surgery for craniosynostosis. I: Isolated craniofacial synostosis : results and unsolved problems

Early surgery for isolated craniosynostosis is designed to improve morphology, to prevent functional disturbances, and equally important, to enhance the psychosocial development of the child. As the first of a two-part series, 104 patients with isolated craniofacial synostosis were retrospectively analyzed. Diagnoses included bilateral coronal (10), unilateral coronal (57), metopic (29), and sagittal synostosis (8). All patients underwent primary fronto-orbital advancement-calvarial vault remodeling procedures at less than 18 months of age (mean 8.1 months). Thirteen percent of patients (14) required a secondary cranial vault operation (mean age 22.6 months) to address residual deficits in craniofacial form. Perioperative complications were minimal (5.0 percent), and there was no mortality. Average length of postoperative follow-up was 46.0 months. By the classification of Whitaker et al., which assesses surgical results, 87.5 percent of patients were considered to have at least satisfactory craniofacial form (category I–II) at latest evaluation. Overall rates of hydrocephalus, shunt placement, and seizures (3.8, 1.0, and 2.9 percent, respectively) were low. Among the isolated craniosynostoses, unilateral coronal synostosis/plagiocephaly poses the most complex problems, including vertical orbital dystopia, nasal tip deviation, and residual craniofacial asymmetry; there is also a wide spectrum of findings and growth patterns in this subgroup.

Evaluation of Pediatric Hydrocephalus by Computed Tomography

Computed tomography (CT) is a safe and reliable technique for the study of children with increased head circumference. Hydrocephalic children requiring drainage of cerebrospinal fluid may be shunted on the basis of the CT scan alone and their postsurgical course followed by serial CT scans thereafter. Any additional pneumographic studies required may be performed via the existing shunt tube, eliminating transcerebral catheterization and its attendant complications.

Twenty-year experience with early surgery for craniosynostosis : II. The craniofacial synostosis syndromes and pansynostosis-Results and Unsolved Problems

As the second of a two-part series, 76 patients with pansynostosis and craniofacial synostosis syndromes were retrospectively analyzed. Diagnoses included pansynostosis (7), craniofrontonasal dysplasia (8), and Apert (24), Crouzon (15), and Pfeiffer (15) syndromes. All patients underwent primary fronto-orbital advancement-calvarial vault remodeling procedures at less than 18 months of age (mean 6.1 months). Twenty-eight patients (36.8 percent) required a secondary cranial vault operation (mean age 28.4 months). Additionally, a major tertiary procedure was necessary in 5 patients to deal with persistent unacceptable craniofacial form. To address the associated finding of midface hypoplasia, 64.8 percent (n = 35) of patients underwent Le Fort III midface advancement or had that procedure recommended for them. The remainder were awaiting appropriate age for this reconstruction. The more extensive pathologic involvement of the pansynostosis and craniofacial syndrome group is illustrated. As compared with the isolated craniofacial synostosis group previously reported, the incidence of major secondary procedures (36.8 versus 13.5 percent), perioperative complications (11.3 versus 5.0 percent), follow-up complications (44.7 versus 7.7 percent), hydrocephalus (42.1 versus 3.9 percent), shunt placement (22.4 versus 1.0 percent), and seizures (11.8 versus 2.9 percent) was significantly increased. Complex problems including those of increased intracranial pressure, airway obstruction, and recurrent turricephaly or cranial vault maldevelopment are repeatedly encountered. In addition, that early fronto-orbital advancement-cranial vault remodeling failed to promote midface development and hypoplasia of this region is almost a consistent finding in the craniofacial syndromic group. The average length of postoperative follow-up was 6 years. According to the classification of Whitaker et al., which assesses surgical results, 73.7 percent of patients were considered to have at least satisfactory craniofacial form (category I–II) at latest evaluation. An algorithmic approach to the treatment of all patients with craniosynostosis is presented utilizing early surgical intervention as the key element.

Intramedullary spinal cord tumors in children

IntroductionPediatric intramedullary spinal cord tumors are rare and make up only a small percentage of all central nervous system neoplasms.DiscussionThese neoplasms are predominantly benign histologically, regardless of size, with a large percentage being astrocytomas or gangliogliomas. Ependymomas, which are common in adults, are relatively uncommon in children. Contemporary management of these tumors has generated much controversy. These neoplasms occur primarily in the cervical region, with pain or a motor deficit as the chief complaint. Surgery on these neoplasms can safely be performed using modern surgical adjuncts such as the ultrasonic aspirator, contact laser and neurophysiological monitoring. A radical resection of these tumors results in a good long-term outcome, since the majority are histologically benign. Adjuvant radiation therapy should only be administered for high-grade or malignant tumors.ConclusionThe majority of spinal cord tumors are benign; however, malignant tumors have a dismal outcome and surgery in these children should be limited to a conservative debulking. An attempt should be made for radical surgery in hope of avoiding radiation and chemotherapy for the benign tumors. Spinal deformity is a concern in these patients since 35% of children may require a stabilization procedure.

Intrinsic brainstem tumors in childhood: surgical indications

Sixty-six children with intrinsic brainstem gliomas diagnosed between 1980 and 1986 underwent radical surgical resection. Retrospective analysis permitted classification of tumors into four categories: diffuse, focal, cystic and cervicomedullary. All 27 patients with diffuse tumors had malignant neoplasms, were not benefitted by surgery and died within 12–18 months. Five of nine cystic tumors, three of five focal tumors and twenty of twenty-four cervicomedullary tumors had low grade histpathology and are alive one to six years postoperatively.The authors propose a clinical-neuroradiological criteria that accurately predict which patients with brainstem tumors are likely to benefit from radical surgical intervention.

Treatment of Intracranial Ependymoma by Surgery Alone

Objective: This study aimed to determine the safety of deferring radiotherapy in pediatric intracranial ependymoma following a radiographically confirmed gross total resection in patients with localized disease. Methods: Children over age 3 were recruited prospectively from 1990 to 1997, following a surgical impression and radiologic confirmation of a gross total resection of an intracranial ependymoma. Results: 10/32 cases of intracranial ependymomas were both eligible and gave consent. 7 remain free of disease without further intervention. 3 recurred, 2 were salvaged with surgery and radiotherapy, none died. Conclusions: Deferral of radiotherapy following gross total resection alone is a safe option in supratentorial ependymomas. The pattern of recurrence is usually local and patients may be salvaged with additional surgery with or without radiotherapy.

Pseudobulbar palsy after posterior fossa operation in children.

The authors describe their experience with an unusual postoperative syndrome of pseudobulbar palsy occurring a few days after the extirpation of large midline vermian/4th ventricular tumors in children. The patients had a delayed onset of supranuclear cranial nerve palsies associated with emotional incontinence and lability that resolved over several weeks to months. It is postulated that retraction pressure on the medial cerebellum and split vermis is the operative insult responsible for edema that subsequently tracked along fiber pathways in the middle and superior cerebellar peduncles into the upper pons and midbrain. Modifications of operative technique to eliminate the need for retraction are presented.

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.

Computed Tomography of Arachnoid Cysts

The typical CT appearance of intracranial arachnoid cysts may obviate additional neuroradiological procedures. Ventriculography using water-soluble contrast media may differentiate a suprasellar arachnoid cyst from a dilated third ventricle. Twelve cases are presented.