Bikash Bose

Neurophysiologic monitoring of spinal nerve root function during instrumented posterior lumbar spine surgery.

Study Design. Retrospective review of 61 consecutive patients. Objectives. To determine the effectiveness of combining intraoperative monitoring of both spontaneous electromyographic activity and compound muscle action potential response to stimulation for detecting a perforation of the pedicle cortex irritation of nerve root during lumbar spine fusion surgery. Summary of Background Data. The complication rate from instrumentation used with lumbar spine fusion varies from 1 to 33%. To prevent neurologic complications, several monitoring techniques have been used to alert surgeons to possible neurologic damage being introduced during nerve decompression or placement of instrumentation with spine procedures. Because of different sensitivities, one monitoring technique may not be as effective for preventing complications as a combination of techniques. Methods. Sixty-one consecutive patients who underwent instrumented posterior lumbar fusions received continuous electromyographic monitoring and stimulus-evoked electromyographic monitoring. A significant neurophysiologic event was signaled by sustained neurotonic electromyographic activity, prompting an alert and a pause in the surgical manipulations that precipitated the activity. After insertion of the transpedicular screws, the integrity of the pedicle cortex was tested by stimulating each screw head and recording compound muscle action potentials. In the presence of a pedicle breach, stimulus intensities below 7 mA were sufficient to evoke compound muscle action potentials from the muscle group innervated by the adjacent spinal nerve root, prompting a surgical alert and subsequent repositioning of the screw. Results. Fourteen significant neurophysiologic events occurred in 13 of 61 patients (21%). Sustained neurotonic electromyographic discharges occurred in 5 of 40 patients during placement of interbody fusion cages, in 2 patients during placement of transpedicular screws, and in 1 patient during tightening of rods. On pedicle screw stimulation, breaches of the pedicle cortex were detected in 6 patients. After surgery, no new neurologic deficits were found in 60 of the 61 patients. One patient who experienced temporary paraparesis had sustained neurotonic electromyographic discharges during retraction of the thecal sac and distraction of the disc space before placement of the cage. Conclusion. These results suggest that intraoperative electromyographic monitoring provides a real-time measure of impending spinal nerve root injury during instrumented posterior lumbar fusion, allowing for timely intervention and minimization of negative postoperative sequela.

Neurophysiological Identification of Position-Induced Neurologic Injury During Anterior Cervical Spine Surgery

This study was a retrospective review of 3,806 patients who underwent anterior cervical spine surgery with multi-modality neurophysiological monitoring consisting of transcranial electric motor evoked potentials, somatosensory evoked potentials and spontaneous electromyography between 1999–2003. The objectives of this study were twofold: (1) to evaluate the role of transcranial electric motor evoked potential tceMEP and ulnar nerve somatosensory evoked potential (SSEP) monitoring for identifying impending position-related stretch brachial plexopathy, peripheral nerve entrapment/compression or spinal cord compression and (2) to estimate the point-prevalence of impending neurologic injury secondary to surgical positioning effects. Sixty-nine of 3,806 patients (1.8% showed intraoperative evidence of impending neurologic injury secondary to positioning, prompting interventional repositioning of the patient. The brachial plexus was the site of evolving injury in 65% of these 69 cases. Impending brachial plexopathy was most commonly noted immediately following shoulder taping and the application of counter-traction. Brachial plexus stretch upon neck extension for optimal surgical access and visualization was second in frequency-of-occurrence. Evolving traction injury to the ulnar nerve attributed to tightly-wrapped or malpositioned arms was observed in 16% of alerted cases, whereas evolving spinal cord injury following neck extension accounted for an additional 19%. This study highlights the role of tceMEP and ulnar nerve SSEP monitoring for detecting emerging peripheral nerve injury secondary to positioning in preparation for and during anterior cervical spine surgery.

Reanalysis of central cervical cord injury management.

Early investigators indicated that conservative management was superior to operative intervention in the treatment of central cord injuries. Their clinical data suggested that operative treatment, in fact, worsened the condition. Recent experience with this clinical entity, however, indicates that in selected patients operative intervention may be of value in improving the rate and degree of motor recovery. A retrospective study of all individuals admitted to our hospital (Delaware Valley Spinal Cord Injury Center) with central cervical spinal cord injury was done (28 patients). One-half had been treated with medical therapy alone (Group I); the others were treated both medically and surgically (Group II). Medical therapy consisted of intravenous mannitol, dexamethasone, and sodium bicarbonate given during the acute phase of the injury. Both groups were immobilized using either a halo or a Philadelphia collar. Criteria for entry into the surgical group were one or both of the following: (a) failure to improve progressively after an initial period of improvement, with persistent compression of neural tissue visualized on myelography and (b) unacceptable instability of the spinal bony elements. The patients were given neurological scores based on the motor power of the major muscle groups. The stability of the spine was scored using the Panjabi-White scale. The two groups were compared using Students t-test and the two-factor analysis of variance. There was no significant difference in initial neurological scores between the groups. The surgical groups had a higher incidence of instability of the bony elements of the cervical spine, as judged by the Panjabi-White scale.(ABSTRACT TRUNCATED AT 250 WORDS)

A reproducible experimental model of focal cerebral ischemia in the cat

In the past experimental methods used for producing focal cerebral ischemia have had considerable difficulty with regard to reproducibility of the size of the infarcted region. In this study we have developed an experimental model which enables us to consistently produce focal regions of cerebral ischemia (resulting in infarction) which vary little in size in a number of animals. Thirty-seven cats (3-4 kg b. wt.) anesthetized with chloralose and urethane were used. Physiologic monitoring and adjustments maintained arterial blood values as follows: pCO2 27-35 Torr, pO2 100-150 Torr, pH +/- 7.4, glucose 200 mg%, hematocrit greater than 25. The left middle cerebral artery was exposed via a transorbital approach and occluded for 1-2 h with and without left and/or both carotid artery occlusion. Sixteen hours following the ischemic episode, the animals were sacrificed and sections of fresh brain tissue were processed for vital staining using 1% tetrazolium solution. With this method normal brain areas appear dark red, ischemic regions (without infarction) appear gray and irreversibly infarcted areas appear pinkish-white. The volumetric dimensions of the lesioned area were measured using a planimeter. The same tissue was also evaluated histologically by means of standard histopathologic techniques on paraffin-embedded material. Infarcted areas as delineated macroscopically by the tetrazolium correlated well with the light microscopic findings. Ten animals subjected to a 2-h occlusion of the left middle cerebral artery (LMCA) and both carotid arteries resulted in a reproducible infarct which was 3.2 +/- 0.7 ml in volume. This represents 13.3 +/- 2.9% of the total volume of both cerebral hemispheres (above the level of the inferior colliculus.(ABSTRACT TRUNCATED AT 250 WORDS)

Ganglioside-induced regeneration and reestablishment of axonal continuity in spinal cord-transected rats

In this study we examined the effect of chronic GM-1 ganglioside treatment on the reestablishment of axonal continuity and functional recovery in spinal cord-transected rats. Previous studies have shown that chronic treatment with GM-1 ganglioside is effective in producing regeneration of lesioned mesostriatal dopaminergic neurons in the central nervous system [1, 2]. In addition, GM-1 ganglioside advances peripheral nerve regeneration following nerve crush injury [12]. Axonal continuity was determined by the ability of the spinal cord to transport horseradish peroxidase across the region of transection. Comparisons between ganglioside-treated and saline-treated controls showed that ganglioside treatment resulted in the reestablishment of axonal continuity between the spinal cord distal to the level of the transection and the brainstem. Saline-treated controls showed little evidence of axonal continuity between these two regions. Thus gangliosides induce reestablishment of axonal continuity and thereby could advance functional recovery in rats following spinal cord transection.

Focal cerebral ischemia: reduction in size of infarcts by ventriculo-subarachnoid perfusion with fluorocarbon emulsion

A new method for brain resuscitation following acute focal ischemic insult has been developed in this laboratory. The technique utilizes a surrogate route to supply cerebral metabolites and employs highly oxygenated fluorocarbons (OFNS), which are efficient gas transport and exchange agents, perfused through the ventriculo-subarachnoid spaces. We previously described a return of aerobic metabolism and EEG after severe global ischemia by oxygenated perfusions and now report treatment-induced reduction in the size of experienced cerebral infarction. Twenty-eight cats were anesthetized (choralose and urethane), tracheotomized and placed in a stereotactic frame. Physiologic adjustments assured arterial blood pCO2 28-35 Torr, pO2 100-150 Torr pH 7.4 and glucose less than 200 mg%. The left middle cerebral artery was exposed transorbitally and temporarily clipped along with both common carotids for 2 h. One hour later (3 h after ischemic onset) the treated group were perfused by the ventriculo-cisternal route either with OFNS [pO2 = 600 Torr; 3 ml/min 6 h, 2 ml/min 2 h, 1 ml/min 2 h, 0.5 ml/min 2 h at 10 mm Hg intracranial pressure (ICP)] or with the vehicle perfusate. Eighteen to twenty hours after the ischemic insult the animals were sacrificed. Sections of fresh brain of 0.5 mm thickness were incubated in 1% triphenyl tetrazolium chloride. The infarcted areas were confirmed with classic neuropathologic techniques. Areas of infarction (expressed in cm3 and as % of the brain) were measured using a planimeter. OFNS-treated brains contained 80% less infarcted tissue than the vehicle-perfused or untreated stroked animals. The infarcted areas were significantly treatment reduced (P less than 0.05 ANOVA and Bonferroni tests).(ABSTRACT TRUNCATED AT 250 WORDS)

Giant basilar artery aneurysm presenting as a third ventricular tumor.

Giant aneurysm of the basilar artery presenting as a 3rd ventricular tumor is an unusual phenomenon. We are reporting a case in which a patient with a giant aneurysm of the basilar artery presented with symptoms of headaches and gait disturbance secondary to obstructive hydrocephalus. Although giant aneurysms presenting as mass lesions have been reported, the computed axial tomographic findings in our case were unique. Giant aneurysms of the basilar artery may be considered in the differential diagnosis of 3rd ventricular tumors.

Preservation of neuronal function during prolonged focal cerebral ischemia by ventriculocisternal perfusion with oxygenated fluorocarbon emulsion.

The left middle cerebral artery and both carotid arteries of 17 cats were occluded to evaluate the effects of oxygenated fluorocarbon emulsion on brain ischemia. Carotid and middle cerebral arteries were occluded concurrently for 2 hours, followed by occlusion of the middle cerebral artery only for another 24 hours. Six animals were treated with oxygenated fluorocarbon emulsion delivered by ventriculocisternal perfusion, 5 received ventriculocisternal perfusion with mock cerebrospinal fluid, and 6 were untreated. Perfusions were started 3 hours after the initial ischemic insult. Infarct size judged by tetrazolium staining and standard neuropathological stains was significantly smaller in the treated animals. The mechanism of protection is as yet unknown, but most likely reflects oxygen/nutrient diffusion into the ischemic middle cerebral artery zone from the ventricular fluorocarbon, or removal of harmful metabolites. The results imply that ventriculocisternal perfusion with fluorocarbon emulsion can preserve neuronal function during a major cerebral vessel occlusion. In the cat, therapy is effective if begun within 3 hours after ischemia starts.

Arachnoiditis presenting as a cervical cord neoplasm: two case reports.

Neurological evaluation supplemented by myelography has been highly successful in diagnosing spinal cord tumors. Our experience shows that a widening of the cord on myelography is not always diagnostic of spinal cord tumors. Two patients who presented clinically with evidence of spinal cord tumor and had a widening of the cord on myelography were found to have severe cervical arachnoiditis without any evidence of intrinsic cord abnormality. Hence, cervical arachnoiditis should be considered in the differential diagnosis of spinal cord tumor on myelography.

Intracerebral hematoma: spontaneous cure by drainage into the middle ear. A case report.

A case of a spontaneous cure of intracerebral hematoma by drainage into the middle ear is reported. A 38-year-old man was brought to the emergency room in a semicomatose state. He was found to have skull fractures and an intracerebral hematoma. His clinical condition improved, and a repeat computed tomographic scan showed disappearance of the hematoma and its replacement by air.