Comparative study of neuroma formation in the rat sciatic nerve after CO2 laser and scalpel neurectomy.

Recent reports have suggested that peripheral neurectomy with the CO2 laser may be effective in preventing subsequent neuroma formation. To study this question further, we performed bilateral sciatic nerve sections in 31 rats using a steel scalpel on one nerve and a CO2 laser on the opposite side. The animals were killed 30 days after neurectomy and specimens were removed for gross observation, light microscopy, and electron microscopy. Axon composition studies were carried out in selected animals and axon diameter histograms were prepared. Well-formed neuromas were present in nerves transected by both the scalpel and the CO2 laser. The scalpel neuromas were characterized by a greater degree of interfascicular collagen deposition and perineurial cell proliferation. Laser neuromas demonstrated less perineurial compartmentalization and scar tissue formation. In addition, a foreign body reaction with multinucleated giant cells surrounding carbonaceous debris was seen that was not present in the scalpel neuromas. Analysis of axon composition studies revealed that both neuromas had a greater density of axons and a higher percentage of small diameter myelinated and unmyelinated axons as compared to control nerves. Laser neuromas had more axons per unit area than scalpel neuromas, but the percentage composition of axons was very similar in the two groups. We could find no evidence in the rat sciatic nerve model that CO2 laser neurectomy is less likely to result in neuroma formation than is conventional scalpel neurectomy.

Effect of mannitol on experimental focal ischemia in awake monkeys.

The effect of mannitol on focal cerebral ischemia in cynomolgus monkeys was studied. After the implantation of a snare ligature about the right middle cerebral artery (MCA) and of deep electrodes for measurement of cerebral blood flow, unanesthetized animals underwent 4-hour MCA occlusion. Ten monkeys were untreated, and 12 animals received mannitol (1.2 g/kg i.v.) 20 minutes after occlusion. The preocclusion and postocclusion deep hemispheric cerebral blood flows (mean CBFs) were similar in the treated and untreated groups. Occlusion produced an average decrease in flow of about 50% in both groups. In the mannitol-treated group the mean CBF of 30.0 fell to 15.8 ml/100 g/minute, and in the untreated group the mean CBF of 29.5 fell to 12.5 ml/100 g/minute. Several animals showed increased CBF after mannitol treatment, and there was an average 21% increase in CBF in the mannitol group after treatment, but this was not a statistically significant difference from the untreated group. With regard to clinical status, there was no significant difference between the mannitol group and the untreated group after MCA occlusion. In individual animals, mannitol treatment caused no significant improvement. Two weeks after occlusion, brains were evaluated for infarct size; there was no significant difference between the mannitol and the untreated groups. In this study, treatment with mannitol (1.2 g/kg) 20 minutes after MCA occlusion failed to modify significantly the mean hemispheric CBF, clinical status, or the pathological effects of 4-hour focal cerebral ischemia.

Chronic spinal epidural hematoma presenting as lumbar stenosis: clinical, myelographic, and computed tomographic features. A case report.

The case of a patient with a chronic spinal epidural hematoma presenting as lumbar stenosis is described. There was no history of major trauma to the lumbar spine, anticoagulant use, or coagulopathy. The clinical, myelographic, and CT findings are presented and discussed.

Effect of naloxone on experimental stroke in awake monkeys.

Naloxone has recently been reported to be of benefit in the treatment of central nervous system ischemia. To study the effect of naloxone in an experimental stroke model, we subjected 40 awake monkeys to middle cerebral artery (MCA) occlusion 2 weeks after the placement of a MCA ligature by a transorbital technique. Cerebral blood flow (CBF) was monitored with stereotactically placed H2 electrodes, and the neurological course was serially recorded. Infarct size was determined 2 weeks after MCA occlusion. Twenty animals served as control and received no naloxone; 10 of these underwent permanent occlusion, and 10 underwent 4-hour MCA occlusion. In 25 treatment animals, naloxone was administered in three different intravenous dosages: (a) naloxone, 2-mg/kg bolus 20 minutes postocclusion and 2 mg/kg/hour X 4 hours, in 10 animals with permanent MCA occlusion; (b) naloxone, 10-mg/kg bolus 20 minutes postocclusion and 10 mg/kg/hour X 4 hours, in 10 animals with 4-hour MCA occlusion; and (c) naloxone, 20-mg/kg bolus, in 5 animals with various neurological deficits. MCA occlusion typically produced a moderate deficit: hemiparesis, hemianopsia, and facial paresis. In most instances, naloxone in the 2- and 10-mg/kg dose regimens produced little or no change in the neurological function. CBF decreased after MCA occlusion and was unaffected by naloxone in most cases. Infarct size was not significantly different between the control and treated groups. However, the 20-mg/kg dose consistently produced a nonfunctional, transient increase in total body motor tone in normal and hemiparetic animals. Naloxone did not significantly improve useful neurological function, CBF, or infarct size in an experimental primate stroke model.

Fibroblastic tumor of the abducens nerve. Case report.

Tumors of the cranial nerves are uncommon, and are usually schwannomas or neurofibromas. The authors describe a case of a fibroblastic tumor involving the sixth cranial nerve. Based upon electron microscopy and immunohistochemistry, the tumor was not of nerve-sheath origin, but was comprised of fibroblasts. Clinical, radiographic, and pathological material are presented, and the literature is discussed. This represents the third case report of a tumor of the abducens nerve, and the first report of a fibroma of a cranial or peripheral nerve.

Congenital dermoid cyst of the anterior fontanel in a Mexican-American.

A congenital inclusion dermoid cyst of the anterior fontanel was removed from a two-year-old Mexican-American female. The cyst had no intracranil extension and was easily excised intact. This is the first report of such a lesion in the Western Hemisphere in a non-black.

Surgical treatment of an abscess in a Rathke's cleft cyst.

An abscess in a Rathke's cleft cyst was surgically treated in a 39-year-old man. The patient presented with headaches, fever, and visual deficits. Transcranial decompression of the optic chiasm was carried out first. The abscess recurred, however, and drainage of the abscess and removal of its wall via the transsphenoidal route was carried out 4 weeks later. Visual evoked responses were useful in the successful management of this lesion. The patient regained normal pituitary function and visual function after the operation.

Transendothelial vesicular transport of protein following compression injury to the spinal cord.

Routes of vascular leakage resulting in trauma-induced edema have not been clarified. To explore the problem we followed the fate of intravascular horseradish peroxidase (HRP) after compression injury to the thoracic cord (cats). At 90 seconds and 15 minutes, HRP was confined to the gray matter, occupying perivascular spaces, unexpanded extracellular channels, and cytoplasmic compartments of injured cells. Adjoining segments contained similar but lesser deposits. At 4 hours, tracer occupied the expanded extracellular spaces of the lesion's white matter; gray matter deposits were present up to 4 cm. distal. Vessels revealed no evidence of rupture. Open interendothelial junctions were not found. Counts of HRP-labeled vesicles in the endothelium of gray matter capillaries revealed a significant intensification of vesicular activity in the lesion and in adjacent areas up to 9 cm. caudal. Morphologically, labeled vesicles exhibited a wide diversity in shape and size. Typical pinocytotic (700A) and tubular forms measured 400 to 700 A in width; vacuolar forms measuring up to 0.7 mum. across were frequently observed. Continuity between the three types was often evident. Where basement membrane and perivascular clefts were not yet inundated with HRP, sites of vesicular emptying of HRP at the tissue front were identified. Serial sections revealed that vesicles may be contiguous from luminal to abluminal surfaces, thus providing facilitated transport pathways. The data suggest that vesicular transport plays a role in the genesis of trauma-induced edema.