Faculty Bibliography

OBJECTIVE AND IMPORTANCE: Although the differential diagnosis of intracranial lesions in patients who have tested positive for human immunodeficiency virus is extensive, toxoplasmosis, lymphoma, and progressive multifocal leukoencephalopathy comprise approximately 90% of such cases. Cytomegalovirus infection of the central nervous system may be difficult to diagnose and rarely presents as mass lesions revealed by radiographic studies. CLINICAL PRESENTATION: Two patients who had tested positive for human immunodeficiency virus presented with progressive focal neurological deficits. Radiographic studies revealed solitary contrast-enhancing lesions in the right basal ganglia and right cerebellar hemisphere, respectively. INTERVENTION: The first patient underwent a stereotactic biopsy but died despite appropriate therapy. The second patient died without tissue having been obtained for diagnosis. Postmortem examinations revealed necrotizing lesions with diffuse areas of infiltrating histiocytes containing eosinophilic cytomegalovirus inclusion bodies. CONCLUSION: Although rare, cytomegalovirus infection should be considered in patients who have tested positive for human immunodeficiency virus and who present with enhancing intracranial lesions

OBJECTIVE AND IMPORTANCE: Intracerebral schwannomas not associated with cranial nerves account for less than 1% of surgically treated schwannomas of the central and peripheral nervous system. Subfrontal schwannomas are extremely rare, with only 15 cases reported to date. CLINICAL PRESENTATION: A 33-year-old man presented with a 4-month history of progressive headaches and lethargy. Radiographic studies revealed a large subfrontal tumor thought to be a meningioma preoperatively. INTERVENTION: The patient underwent a craniotomy for resection of his tumor. Intraoperatively, a large extra-axial tumor arising from the floor of the left frontal fossa was encountered. CONCLUSION: Microscopic examination of the tumor revealed a schwannoma. Several theories on the possible origin of intracerebral schwannomas have been considered. Because of the age of the patient at presentation, many authors have postulated a developmental origin for these lesions. However, extra-axial schwannomas not associated with cranial nerves often present later in life, suggesting a different pathogenesis for this subgroup

We present an unusual case of a craniopharyngioma with a visual field deficit related to optic tract compression by the anterior cerebral artery. The presentation and management of this case are described. Previous cases of visual field deficits associated with craniopharyngiomas are reviewed

The detrimental effects of extreme blood gas values are well documented. However, the range of normal values has not been rigorously defined. There is an ongoing debate concerning the need for ventilation and tight control of blood gas values in spinal cord injury models. Consequently, we performed a retrospective study of 84 rats using a graded rat spinal cord contusion model. Spinal cord ionic lesion volumes were calculated from Na and K shifts at 24 h after injury. Blood gas measurements were obtained 5 min before contusion. For pH values of 7.31-7.46, systemic acidosis was associated with a small but significant decrease in ionic lesion volumes in the 12.5 and 25 g.cm contusion groups (p < 0.05 and p < 0.03, respectively). pH had no effect on ionic lesion volumes in the 50 g.cm contusion group (p > 0.5). PaCO2 values from 23 to 53 mm Hg showed an effect only at 25 g.cm (p < 0.05). PaO2 values of 46-138 mm Hg and calculated HCO3 values of 13-28 mEq/L had no effect on ionic lesion volumes. Two conclusions may be derived from these data. First, mild systemic acidosis is associated with a small reduction in ionic lesion volumes after mild and moderate injury but not after severe injury. This suggests that secondary mechanisms play a greater role in mild injuries. Second, variations in arterial blood gases within clinically normal ranges do not strongly influence 24-h ionic lesion volumes in a graded spinal cord injury model. The effects of blood gas values on ionic lesion volumes are not statistically significant unless the data are adjusted for injury severity. Although blood gas values must be carefully monitored, ventilation may not be needed routinely in rat spinal cord injury models. We recommend maintaining pH values between 7.35 and 7.40, PaCO2 between 35 and 41 mm Hg, and PaO2 greater than 71 mm Hg

Tonsillar descent of the cerebellum in Chiari I malformations is often considered a congenital defect. A patient is presented in whom magnetic resonance (MR) imaging revealed normally positioned cerebellar tonsils; however, 1 year later MR imaging was repeated for evaluation of gait abnormalities and showed descent of the cerebellar tonsils. This case illustrates worsening symptoms with progressive descent of the cerebellar tonsils and suggests that Chiari I malformations can evolve postnatally

OBJECTIVE: The association of human immunodeficiency virus with a clinical picture of motor neuron disease is uncommon, with three cases reported to date. This case represents an additional case of a human immunodeficiency virus-infected patient with apparent motor neuron disease. DESIGN: Single patient case report. SETTING: Large urban public hospital. PATIENT: A 45-year-old human immunodeficiency virus-positive Hispanic man who presented with muscle wasting, fasciculations, areflexia, cranial nerve deficits, and weakness progressing to a complete quadriplegia. RESULTS: Electrophysiologic data showed evidence of diffuse denervation with normal sensory and motor nerve conductions and no evidence of demyelination. Electromyography showed diffuse sharp waves and fibrillation. CONCLUSIONS: This case demonstrates a progressive motor neuron dysfunction in a patient positive for the human immunodeficiency virus and provides additional evidence that infection with the human immunodeficiency virus should be considered in the differential diagnosis of apparent motor neuron disease

Pediatric meningiomas are uncommon. Those presenting in the third ventricle are rare; there are only 15 cases reported in the literature. We report an additional third ventricular meningioma in a 6-year-old boy. The tumor was resected via an anterior transcallosal interfornicial approach. Postoperatively, the patient exhibited a transient episode of mutism. Unlike previous reports, the pathological diagnosis of this lesion was an atypical meningioma. The presentation, management, pathological features, and postoperative course of our case are discussed and compared with previous reports

We report a case of radiation necrosis occurring 47 years after resection and radiotherapy for a juvenile pilocystic cerebellar astrocytoma, the longest yet reported. The patient presented with progressive lower cranial nerve dysfunction, and eventually died from cardiopulmonary arrest secondary to aspiration. The presentation, diagnosis, pathological features, and management of radiation necrosis are discussed

Intramedullary spinal cord abscesses are relatively uncommon. We report the first case of an intramedullary spinal cord abscess in a preexisting spinal cord ependymoma. The clinical features and pathogenesis are discussed. Salient features of the management of intramedullary spinal cord abscesses are outlined

Oligodendrocyte transplantation into the retina enables us to investigate the early events in myelin formation in a new in vivo system. The axons of rat retinal ganglion cells are unmyelinated in the eye but should express a myelination initiation signal since they acquire myelin posterior to the globe. The lamina cribrosa may block the migration of oligodendrocytes from the optic nerve into the retina. Animals that lack a lamina cribosa such as the rabbit have myelinated retinas. We have bypassed the lamina cribrosa by using transplantation techniques and inserted freshly isolated syngeneic 3-week-old rat oligodendrocytes into the unmyelinated 4-day-old rat retina during the period of active optic nerve myelination. The animals are sacrificed at 1-week intervals for 8 weeks. The retinas are examined immunocytochemically for myelin with an antibody to myelin basic protein (MBP). MBP-positive cells are seen extending processes at 1 and 2 weeks. Three and four week retinas show the formation of thicker and longer myelin sheaths oriented along the same radial path as the retinal ganglion axons with maximal MBP staining intensity seen by 5 weeks. Transplanted retinas are negative when stained for P0, a Schwann cell antigen, ruling out Schwann cell myelination of our retinas. We have shown that rat cerebral oligodendrocytes survive, mature, and express a myelin-specific protein in the retinal environment in a pattern consistent with myelination of ganglion cell axons. Retinal transplantation provides a new in vivo model to study oligodendrocyte development and axonal-glial interactions, free from the difficulties inherent in culture systems