Z. Harry Rappaport

There are no satisfactory animal models of trigeminal neuralgia, and it is difficult to obtain essential data from patients. However, trigeminal neuralgia presents with such idiosyncratic signs and symptoms, and responds to so distinctive a set of therapeutic modalities, that scientific deduction can be used to generate likely hypotheses. The ignition hypothesis of trigeminal neuralgia is based on recent advances in the understanding of abnormal electrical behavior in injured sensory neurons, and new histopathologic observations of biopsy specimens from patients with trigeminal neuralgia who are undergoing microvascular decompression surgery. According to the hypothesis, trigeminal neuralgia results from specific abnormalities of trigeminal afferent neurons in the trigeminal root or ganglion. Injury renders axons and axotomized somata hyperexcitable. The hyperexcitable afferents, in turn, give rise to pain paroxysms as a result of synchronized afterdischarge activity. The ignition hypothesis accounts for the major positive and negative signs and symptoms of trigeminal neuralgia, for its pathogenesis, and for the efficacy of treatment modalities. Proof, however, awaits the availability of key experimental data that can only be obtained from patients with trigeminal neuralgia.

OBJECT: Recent progress in the understanding of abnormal electrical behavior in injured sensory neurons motivated an examination, at the ultrastructural level, of trigeminal roots of patients with trigeminal neuralgia (TN). METHODS: In 12 patients biopsy specimens of trigeminal root were obtained during surgery for microvascular decompression. Pathological changes in tissue included axonopathy and axonal loss, demyelination, a range of less severe myelin abnormalities (dysmyelination), residual myelin debris, and the presence of excess collagen, including condensed collagen masses in two cases. Within zones of demyelination, groups of axons were often closely apposed without an intervening glial process. Pathological characteristics of nerve fibers were clearly graded with the degrees of root compression noted at operation. Pain also occurred, however, in some patients who did not appear to have a severe compressive injury. CONCLUSIONS: Findings were consistent with the ignition hypothesis of TN. This model can be used to explain the major positive and negative symptoms of TN by axonopathy-induced changes in the electrical excitability of afferent axons in the trigeminal root and of neuronal somata in the trigeminal ganglion. The key pathophysiological changes include ectopic impulse discharge, spontaneous and triggered afterdischarge, and crossexcitation among neighboring afferents.

Objective To establish the safety of intravenous dexanabinol in severe head injury. Design Prospective, randomized, double-blind, placebo- (vehicle) controlled, multicenter, escalating dose study of a single administration of drug (48 or 150 mg) or vehicle (1 or 3 mL). Setting All Israeli neurosurgical intensive care units (a total of six units). Patients Sixty-seven patients, aged 16–65 yrs, Glasgow Coma Scale score of 4–8, injured within 6 hrs of treatment. Measurements and Main Results Intracranial pressure, cerebral perfusion pressure, blood pressure, and heart rate were measured continuously in the intensive care unit. Adverse medical events were recorded and clinical outcome was assessed by the Glasgow outcome scale throughout a 6-month follow-up period. A highly significant reduction in the percentage of time with intracranial pressure >25, cerebral perfusion pressure <50, and systolic blood pressure <90 mm Hg was observed in the drug-treated group. The nature and incidence of adverse medical events were similar in the two groups. The percentage of patients achieving good neurologic outcome on the Glasgow outcome scale was 21% and 14% higher in the drug-treated group at 3 and 6 months, respectively. Statistical analysis of these differences by a logistic model using dose, entry Glasgow coma scale score, and computed tomograph as covariates yielded p values for the effect of treatment of .03 and .14 at 3 and 6 months, respectively. Conclusions Dexanabinol was safe and well tolerated in severe head injury. The treated patients achieved significantly better intracranial pressure/cerebral perfusion pressure control without jeopardizing blood pressure. A trend toward faster and better neurologic outcome was also observed.

Middle cerebral artery occlusions (MCAo) in rats produce infarcts in the pyriform and frontoparietal cortex, extending into the lateral basal ganglia and parasagittal cortex. We estimated tissue H2O concentrations from wet and dry weight measurements and determined Na and K concentrations by atomic absorption spectroscopy in these areas of rat brains. Tissue samples were analyzed at 2, 4, and 24 hours after MCAo and sham MCAo, compared with normal values measured in unoperated rats. In the pyriform and frontoparietal areas, H2O concentrations increased to 34 and 7% greater than normal by 2 hours, and 89 and 94% by 24 hours after MCAo. Na concentrations rose in these areas to 73 and 37% greater than normal by 2 hours, and 281 and 330% by 24 hours. K concentrations did not change until 4 hours, but fell to 62 and 34% of normal in these areas by 24 hours. Such large ion shifts indicate severe tissue destruction. In the parasagittal cortex and basal ganglia areas, the ion and water changes were smaller and did not become significant until 24 hours after MCAo. Rates of Na entry into the infarct site were greatest at 0-2 hours, while the rates of K loss peaked later, between 2 and 4 hours. The difference in Na influx and K efflux resulted in net ion shifts that correlated highly with water entry, yielding a correlation coefficient of 0.992 (p less than 0.001) and a slope indicating that 1 ml of water entered the tissue with each 145 mumoles of ions. These findings strongly suggest that net ion shifts cause the early edema of regional brain ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

OBJECTIVE: To evaluate the nasal complications after transnasal transsphenoidal operations for pituitary tumors, comparing two surgical techniques: traditional sublabial transseptal and endoscopic transseptal techniques. STUDY DESIGN: We retrospectively evaluated by self-reported questionnaire and endoscopic examination the nasal condition of 40 consecutive patients with pituitary tumors: 20 patients had endoscopic surgery and 20 had surgery with the traditional sublabial technique. RESULTS: Compared with the traditional technique, the endoscopic approach was associated with a shorter operative time (about 40 min), shorter hospitalization time (about half), absence of recurrent epistaxis snoring and denture problems, and lower incidence of septal perforation, synechia, and crust formation. Furthermore, loss of nasal tip projection was found only in the group that had surgery with the sublabial technique. CONCLUSIONS: Endoscopically guided transseptal transsphenoidal surgery is simple to perform and time-saving, and it results in fewer nasal and denture complications than the sublabial technique. At the same time, it allows the surgeon all the benefits of the binocular microscopic surgical field that are associated with the traditional approach.