Ali R. Rezai

Complications of deep brain stimulation surgery

Although technological advances have reduced device-related complications, DBS surgery still carries a significant risk of transient and permanent complications. We report our experience in 86 patients and 149 DBS implants. Patients with Parkinson’s disease, essential tremor and dystonia were treated. There were 8 perioperative, 8 postoperative, 9 hardware-related complications and 4 stimulation-induced side effects. Only 5 patients (6%) sustained some persistent neurological sequelae, however, 26 of the 86 patients undergoing 149 DBS implants in this series experienced some untoward event with the procedure. Although there were no fatalities or permanent severe disabilities encountered, it is important to extend the informed consent to include all potential complications.

Comparison of anatomic and neurophysiological methods for subthalamic nucleus targeting.

OBJECTIVE The subthalamic nucleus (STN) has recently become the surgical target of choice for the treatment of medically refractory idiopathic Parkinsons disease. A number of anatomic and physiological targeting methods have been used to localize the STN. We retrospectively reviewed the various anatomic targeting methods and compared them with the final physiological target in 15 patients who underwent simultaneous bilateral STN implantation of deep brain stimulators. METHODS The x, y, and z coordinates of our localizing techniques were analyzed for 30 STN targets. Our final targets, as determined by single-cell microelectrode recording, were compared with the following: 1) targets selected on coronal magnetic resonance inversion recovery and T2-weighted imaging sequences, 2) the center of the STN on a digitized scaled Schaltenbrand-Wahren stereotactic atlas, 3) targeting based on a point 13 mm lateral, 4 mm posterior, and 5 mm inferior to the midcommissural point, and 4) a composite target based on the above methods. RESULTS All anatomic methods yielded targets that were statistically significantly different (P < 0.001) from the final physiological targets. The average distance error between the final physiological targets and the magnetic resonance imaging-derived targets was 2.6 +/- 1.3 mm (mean +/- standard deviation), 1.7 +/- 1.1 mm for the atlas-based method, 1.5 +/- 0.8 mm for the indirect midcommissural method, and 1.3 +/- 1.1 mm for the composite method. Once the final microelectrode-refined target was determined on the first side, the final target for the contralateral side was 1.3 +/- 1.2 mm away from its mirror image. CONCLUSION Although all anatomic targeting methods provide accurate STN localization, a combination of the three methods offers the best correlation with the final physiological target. In our experience, direct magnetic resonance targeting was the least accurate method.

Neurophysiological refinement of subthalamic nucleus targeting.

OBJECTIVEAdvances in image-guided stereotactic surgery, microelectrode recording techniques, and stimulation technology have been the driving forces behind a resurgence in the use of functional neurosurgery for the treatment of movement disorders. Despite the dramatic effects of deep brain stimulation (DBS) techniques in ameliorating the symptoms of Parkinson’s disease, many critical questions related to the targeting, effects, and mechanisms of action of DBS remain unanswered. In this report, we describe the methods used to localize the subthalamic nucleus (STN) and we present the characteristics of encountered cells. METHODS Twenty-six patients with idiopathic Parkinson’s disease underwent simultaneous, bilateral, microelectrode-refined, DBS electrode implantation into the STN. Direct and indirect magnetic resonance imaging-based anatomic targeting was used. Cellular activity was analyzed for various neurophysiological parameters, including firing rates and interspike intervals. Physiological targeting confirmation was obtained by performing macrostimulation through the final DBS electrode. RESULTS The average microelectrode recording time for each trajectory was 20 minutes, with a mean of 5.2 trajectories/patient. Typical trajectories passed through the anterior thalamus, zona incerta/fields of Forel, STN, and substantia nigra-pars reticulata. Each structure exhibited a characteristic firing pattern. In particular, recordings from the STN exhibited an increase in background activity and an irregular firing pattern, with a mean rate of 47 Hz. The mean cell density was 5.6 cells/mm, with an average maximal trajectory length of 5.3 mm. Macrostimulation via the DBS electrode yielded mean sensory and motor thresholds of 4.2 and 5.7 V, respectively. CONCLUSION The principal objectives of microelectrode recording refinement of anatomic targeting are precise identification of the borders of the STN and thus determination of its maximal length. Microelectrode recording also allows identification of the longest and most lateral segment of the STN, which is our preferred target for STN DBS electrode implantation. Macrostimulation via the final DBS electrode is then used primarily to establish the side effect profile for postoperative stimulation. Microelectrode recording is a helpful targeting adjunct that will continue to facilitate our understanding of basal ganglion physiological features.

The Interactive Use of Magnetoencephalography in Stereotactic Image-guided Neurosurgery

OBJECTIVE To expand the use of magnetoencephalography (MEG) functional mapping in the operating room as well as preoperatively, a method of integrating the MEG sensorimotor mapping information into a stereotactic database, using computed tomographic scans, magnetic resonance imaging scans, and digital angiography, was developed. The combination of functional mapping and the stereotactic technique allows simultaneous viewing of the spatial relationship between the MEG-derived functional mapping, the radiological/structural anatomic characteristics, and the pathological abnormality. METHODS MEG data were collected using a MAGNES II Biomagnetometer and were incorporated into the COMPASS frame-based and REGULUS frameless stereotactic systems. The transformation process, by calculating a translational vector and a rotation matrix, integrates functional and anatomic information that is then directly available intraoperatively in the stereotactic database. This procedure was employed in 10 patients undergoing computer-assisted stereotactic volumetric resections for lesions involving the sensorimotor cortex. The principles of coregistration and coordinate transformation are reviewed in the context of preoperative functional mapping. We introduce innovations to apply these techniques to intraoperative stereotactic systems. RESULTS Tests of the accuracy of the intraoperative integration of functional information in patients and calibration phantoms indicated close agreement with earlier preoperative methods. The intraoperative availability of functional information was a significant aid to the surgeon because it provided more accurate information on the location of functional tissue than could be derived solely by radiological criteria. CONCLUSION The real-time availability of functional mapping information in an interactive fashion can reduce surgical risk and minimize functional morbidity. Within the ever-expanding realm of functional mapping and image-guided neurosurgery, further progress and integration of these methods is critical for resection of lesions involving eloquent cortex.

Contemporary management of spinal osteomyelitis.

OBJECTIVE We review the results of treatment of a series of patients with spinal osteomyelitis, to formulate a systematic and comprehensive approach to the management of this disease in light of recent technical and conceptual advances in imaging, spinal biomechanics, and internal fixation. METHODS We retrospectively reviewed the records for 57 consecutive patients with pyogenic spinal osteomyelitis who were treated between June 1987 and June 1995. Pain and weakness were the most common presenting symptoms. The mean duration of symptoms at the time of diagnosis was 10.6 weeks. Surgical indications included the presence or development of motor deficits with epidural compression and/or localized kyphotic deformities or the failure of medical therapy. RESULTS Thirty-three patients underwent surgery as their initial treatment. Six additional patients experienced medical therapy failure and received subsequent surgical treatment. Seventeen patients were treated using an anterior approach only, 13 were treated using a posterior approach only, and 9 were treated using a combined anterior and posterior approach. After a minimal follow-up period of 24 months, 93% of the surgically treated patients showed neurological improvement or were neurologically intact, with a mean 16-degree decrease in localized kyphotic deformities and with solid bony fusion and resolution of pain for all patients. CONCLUSION Early surgical decompression results in rapid improvement of neurological deficits, decreases in kyphotic deformities, and stabilization with bony fusion. The presence of active infection does not preclude the use of internal fixation. Nonsurgical management is indicated for patients with minimal or no neurological deficits and the absence of significant localized kyphotic deformities. However, 25% of patients who were initially treated nonsurgically experienced medical therapy failure and underwent surgical treatment.

Magnetoencephalographic mapping: Basis of a new functional risk profile in the selection of patients with cortical brain lesions

OBJECTIVE Surgical management of cortical lesions adjacent to or within the eloquent cerebral cortex requires a critical risk: benefit analysis of the procedure before intervention. This study introduced a measure of surgical risk, based on preoperative magnetoencephalographic (MEG) sensory and motor mapping, and tested its value in predicting surgical morbidity. METHODS Forty patients (21 men and 19 women; mean age, 36.5 yr) with cortical lesions (12 arteriovenous malformations and 28 tumors) in the vicinity of the sensorimotor cortex were classified into high-, medium-, or low-risk categories by using the MEG-defined functional risk profile (FRP). This was based on the minimal distance between the lesion margin and the sensory and motor MEG sources, superimposed on a magnetic resonance imaging scan. Case management decisions were based on the MEG mapping-derived FRP in combination with biopsy pathological findings, radiographic findings, and anatomic characteristics of the lesion. A recently developed protocol was used to transform MEG source locations into the stereotactic coordinate system. This procedure provided intraoperative access to MEG data in combination with stereotactic anatomic data displays routinely available on-line during surgery. RESULTS It was determined that 11 patients diagnosed as having gliomas had high FRPs. The margin of the lesion was less than 4 mm from the nearest MEG dipole or involved the central sulcus directly. A nonoperative approach was used for six patients of this group, based on the MEG mapping-derived FRP. In the group with arteriovenous malformations, 6 of 12 patients with high or medium FRPs underwent nonoperative therapy. The remaining 28 patients, whose lesions showed satisfactory FRPs, underwent uneventful lesion resection, without postoperative neurological deficits. CONCLUSION Our results suggest that MEG mapping-derived FRPs can serve as powerful tools for use in presurgical planning and during surgery.

Nonneoplastic intramedullary spinal cord lesions mimicking tumors

OBJECTIVE We report a group of nine patients with atypical, nonneoplastic intramedullary spinal cord lesions. By retrospectively reviewing these patients, we hoped to elucidate characteristics that would identify these patients as harboring nonneoplastic lesions before surgical intervention. METHODS We reviewed the histological findings of 212 patients undergoing surgery for intramedullary spinal cord tumors between 1989 and 1994. We identified nine patients with nonneoplastic lesions (4%); case histories and radiographs were reviewed. RESULTS All patients were evaluated preoperatively using magnetic resonance imaging. The extent of enhancement with gadolinium varied from homogeneous enhancement to no enhancement. All lesions showed marked T2 changes. There was a lack of significant spinal cord expansion associated with the lesions in all cases. All patients underwent surgery. The histology of the surgical specimens showed demyelinating lesions in four patients, sarcoidosis in two patients, amyloid angiopathy in two patients, and a mass of nonneoplastic inflammatory cells of unknown origin in one patient. CONCLUSION Although it was difficult to antecedently distinguish these lesions from neoplastic spinal cord tumors by case history and physical examination, the most consistent clue was absent or minimal spinal cord expansion on the preoperative magnetic resonance images.

Acute Surgical Management of Intracranial Arteriovenous Malformations

The majority of intracranial arteriovenous malformations (AVMs) do not require acute surgical intervention. Some patients, however, require emergent surgical treatment because of a profound neurological deterioration from a mass effect. We report 10 patients who underwent emergency AVM surgery after experiencing neurological deterioration from an intracranial hemorrhage. Two patients bled spontaneously, whereas eight had an intracranial hemorrhage secondary to an embolization procedure. When the patients demonstrated neurological deterioration, they were intubated, hyperventilated, and underwent osmotic diuresis. Barbiturate anesthesia was initiated, and surgery was performed within 30 minutes in most cases. The hematomas were evacuated, and an attempt was made to excise the AVMs at the same time. Postoperatively, intracranial pressure was monitored, and barbiturate coma was maintained until the intracranial pressure returned to normal. Cerebral perfusion pressure was maintained above 55 mm Hg. The operation was confined to evacuating the hematoma in two patients with inoperable AVMs. The other eight patients underwent concomitant total AVM resection. Because of the severity of neurological deterioration, one patient who bled spontaneously underwent surgery based only on a computed tomographic scan of the brain. Nine patients made a good-to-excellent recovery. One patient with a large motor-strip AVM remained hemiplegic. We conclude that in patients presenting with profound neurological deterioration after a spontaneous intracranial hemorrhage or one associated with an embolization procedure, prompt hematoma evacuation with simultaneous AVM excision as well as perioperative intracranial pressure control with mannitol and barbiturates can yield a good-to-excellent outcome.

Sigmoid Diverticular Perforation in Neurosurgical Patients Receiving High-Dose Corticosteroids

Perforation of colonic diverticula is a complication of corticosteroid use that has not been described in the neurosurgical literature. Between 1987 and 1992, 719 patients who underwent surgery for primary and metastatic brain and spinal tumors of the central nervous system received 2246 to 4936 mg of methylprednisolone given over at least 7 days. Five patients in this group (all men, ages 50-69 yr) experienced a sigmoid diverticular perforation at a mean dose of 3947 mg of methylprednisolone (range, 2240-6160 mg). Of these five, two had a known history of diverticular disease. In contrast, during this same period, 3749 patients who underwent neurosurgical procedures for non-neoplastic conditions did not receive corticosteroids and experienced no colonic perforations. All five patients with colonic perforations presented with abdominal pain and had free intraperitoneal air that was revealed on radiographs of the abdomen. Perforation of a sigmoid diverticulum was confirmed in all five at exploratory laparotomy. Four patients had good outcomes, and one died. We conclude the following: 1) patients over age 50 who receive high-dose corticosteroids are at risk for sigmoid colonic perforation, and these medications should be used with caution in such patients; 2) if possible, lower total doses of perioperative corticosteroids should be used in patients with known diverticular disease; and 3) because corticosteroids mask many of the inflammatory signs of perforation, this diagnosis should be considered in any patient with abdominal discomfort, fever of unknown origin, or unexplained leukocytosis.

Traumatic posterior cerebral artery aneurysm secondary to an intracranial nail: Case report

We present the case of a traumatic posterior cerebral artery aneurysm from a self-inflicted pneumatic nail-gun missile injury through the roof of the mouth. The patient presented to us in a coma with subarachanoid and intraventricular hemorrhage. Cerebral angiography revealed an aneurysm of the left posterior cerebral artery with no distal filling. The patient died 6 days after admission. At autopsy, a pseudoaneurysm of the posterior cerebral artery was seen. This aneurysm resulted from direct disruption of the arterial wall by the intracranial nail.