George W. Sypert

Evoked potential monitoring during aneurysm operation: observations after fifty cases.

Somatosensory or brain stem auditory evoked potentials (EPs) were monitored during 50 aneurysm procedures. Base line EPs were obtained shortly after the induction of general anesthesia and were recorded continuously during operation. Absolute latency, interpeak latency, and cortical EP amplitude were subsequently determined. Statistical analysis confirmed that significant changes in these parameters are routine during aneurysm operation. Arbitrary definitions of abnormal latency and amplitude changes led to an excessive false-positive/false-negative rate. From the time of dural opening to the time of closure, prolongation of central conduction time, decrease in cortical amplitude, or disappearance of the EP was predictive of postoperative sensory or motor deficit in all patients monitored, except those undergoing operation on basilar artery aneurysms. In basilar aneurysm cases, outcome could not be reliably predicted with either EP technique.

Cervical Carotid Dissecting Aneurysms

Thirteen cases of cervical carotid dissecting aneurysm have been seen at the University of Florida during the past 3 years. In our experience, two groups of patients with this disease can be distinguished clearly by either clinical or angiographic criteria. One group of cervical carotid dissecting aneurysms is characterized by spontaneous onset, unilaterality, and the absence of pseudoaneurysm formation. These lesions have a strong tendency to resolve with appropriate medical therapy. The other group is characterized by an association with obvious predisposing factors, such as fibromuscular dysplasia, angiography, or trauma. These lesions are often associated with pseudoaneurysms and rarely resolve spontaneously. These two groups of lesions probably represent a spectrum of the same basic disease process. The natural history of patients who survive a cervical carotid dissection is usually one of stability or improvement. A trial of medical therapy (to prevent embolic symptoms) and repeat arteriography are indicated before the consideration of surgical therapy.

Intramedullary spinal tuberculoma.

A case report of intramedullary spinal tuberculomas presenting as cervical myelopathy is described. The rarity of these lesions in North America make this case unique. The use of modern neurodiagnostic and microsurgical techniques as well as the use of postoperative antituberculous drugs resulted in a good outcome. The first known description of magnetic resonance imaging of intramedullary spinal tuberculomas is presented. The gross and microscopic appearances of the lesion are given.

Successful treatment of the normal perfusion pressure breakthrough syndrome

Massive, multifocal bleeding after the technically successful removal of a cerebral arteriovenous malformation (AVM) represents a frightening and usually catastrophic complication. This phenomenon, termed normal perfusion pressure breakthrough by Spetzler et al., is caused by the diversion of blood flow from the AVM into adjacent, maximally dilated, and nonautoregulating small vessels. We recently encountered three cases of cerebral AVM that exhibited breakthrough bleeding immediately after an apparently successful operation. In all cases, the surgeon was unable to control the resultant hemorrhage by standard microsurgical techniques. High dose barbiturate anesthesia, combined with blood pressure reduction to the lower levels of the normal cerebral perfusion curve, was then initiated in each case. Controlled hyperventilation, steroids, and osmotic dehydrating agents were also used to control intracranial pressure elevation. After maintenance of this regimen for several days, the patients were returned to the operating room for hematoma evacuation. At this time, bleeding was controlled easily and breakthrough did not occur. Although this regimen requires intensive anesthetic, pulmonary, and cerebral monitoring, it successfully salvaged all three patients. Two made immediate, remarkable recoveries, and the third patient is slowly improving. This protocol therefore seems promising for the management of the massive, uncontrollable cerebral swelling or bleeding that may occur as a consequence of AVM removal.

Independent evaluation of a multidisciplinary rehabilitation program for chronic low back pain

Severe chronic low back pain was diagnosed in 236 patients by one physician and they were referred to the University of Miami Comprehensive Pain and Rehabilitation Center (UMCPRC) over a 5-year period for an intensive 4-week inpatient treatment program. Of these 143 (61%) were able to be contacted by telephone and given a structured interview designed for the study. The average time elapsed at follow-up from referral for all patients was 22.5 months. Outcome was measured in the following terms: current levels of pain, percent decrease in pain, subsequent health care utilization, activities of daily living, and attitudes toward treatment. After completion of the interview, the McGill Pain Questionnaire and the Oswestry Low Back Pain Disability Questionnaire were sent to the patients. The patients fell into five groupings: Group 1--participants in the UMCPRC program (n = 39); Group 2--those whose participation was not approved by insurance (n = 30); Group 3--those who declined participation (n = 46); Group 4--participants in other programs (n = 14); Group 5--dropouts (n = 14). The five groups were not meaningfully different with regard to prereferral demographics. Interestingly, Group 1 patients exhibited significantly greater prereferral pain and unemployment levels. Despite this, at follow-up significantly more Group 1 members were employed and they exhibited a greater percent decrease in pain as compared to the nonparticipant groups. Returned McGill and Oswestry Questionnaires mirrored these findings. Group 1 members also demonstrated significantly lower rates of subsequent health care utilization, i.e., physician visits, hospitalizations, and surgery than the nonparticipant groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Transoral approach to the upper cervical spine

The transoral approach to pathology of the upper cervical spine is logical, but it is seldom used due to concerns about exposure and infection. The authors report on 16 consecutive patients requiring exposure from clivus through C3 for pathology, including spinal cord compression by rheumatoid pan‐nus, craniovertebral anomalies, and tumor. Exposure was obtained using a Dingman mouth gag and soft palate retraction with silicone rubber sheeting. A horizontal “H” incision was made in the posterior pharyngeal wall creating three layers, closed separately, with attention to a watertight closure of the final mucosal layer. In no case was it necessary to divide the mandible, tongue, soft palate, or uvula. There were no deaths, wound breakdowns, infections, or persistent cerebrospinal fluid leakage. Patients with neurological indications improved postopera‐tively, and all tumors were grossly resected.

Histopathology of the ferric-induced chronic epileptic focus in cat: A Golgi study

Abstract Five cats were rendered chronically epileptic via subpial injection of saturated FeCl 3 solution. Six weeks postinjection, electrocorticographic recording demonstrated focal epileptiform spiking in the region of the injection. This finding was not observed in saline-injected controls. Histopathological analysis of the epileptic focus using Nissl and Golgi-Cox techniques revealed (i) depopulation of Golgi-impregnated neurons, (ii) astocytic gliosis, (iii) loss of dendritic spines, (iv) decreased dendritic branching, and (v) dendritic varicosities. These are similar to the pathological findings which have been described for human epileptogenic foci. These results, in combination with the frequent observation of hemosiderosis in regions of human epileptogenic foci, implicate the release of iron from extravasated blood elements as a possible etiologic mechanism. Therefore, we believe the FeCl 3 experimental epileptogenic focus accurately models the human clinical entity (posttraumatic epilepsy) with respect to both electrophysiology and histopathology.

Basis of segmental motor control: motoneuron size or motor unit type?

The principles of organization of motor control at the segmental level are developed and discussed in this review. Consideration is given to the concepts of the motor unit, and the motoneuron pool. Recent studies from our laboratories that have significance for hypotheses regarding segmental motor control are presented. These studies indicate that the critical factor controlling motor unit recruitment in heterogenous muscles is motor unit type. This results in motor unit recruitment in the order of increasing contraction strength and fatigability: slow twitch, fatigue-resistant first; fast twitch, fatigue-resistant second; fast twitch with intermediate fatigue resistance third; and fast twitch, fatigable units last. A recruitment model that incorporates this hypothesis is presented in which there is an orderly recruitment of motor units by type. This recruitment model, based on data from cat medial gastrocnemius motor units, closely approximates a theoretical optimal recruitment strategy and is consistent with actual medial gastrocnemius muscle forces generated during free movements in intact animals.

Dendritic alterations in rat isocortex within an iron-induced chronic epileptic focus.

Ferrous chloride was injected into the rat isocortex in 5-microliters volumes as an aqueous solution with a concentration of 100 mM. Bursts of epileptiform discharges were sustained throughout the 6 weeks of observation. Nissl and Golgi-Cox stains showed gliosis and neuronal loss within the injection site. Neurons adjacent to the cavitory lesion showed deformity of dendrites, dendritic nodularity, loss of spines, and string-of-beads deformity. These changes are identical to those found in human epileptogenic foci.

Angiographically cryptic cerebrovascular malformations.

Three cases of angiographically cryptic cerebrovascular malformations are presented and a review of the cases in the English literature is tabulated. The typical patient is a 30- to 40-year-old woman with a history of seizures and headache. There is no antecedent history suggesting hemorrhage. On nonenhanced computerized tomographic scans, these lesions are denser than normal brain. They enhance with contrast administration. The angiogram demonstrates an avascular mass. The history, physical findings, and radiographic studies suggest brain tumor. An accurate diagnosis requires operation and pathological examination of the lesion.