Cases of the Month, October to December 2002

The October 2002 Case of the Month (COM). The patient was a 27‐year‐old woman with a history of partial complex seizures at age 7. At age 20 her seizures changed in character and became progressively worse. Neuroimaging studies showed atrophy of the right hemisphere and contralateral cerebellar atrophy. Following a biopsy, she was scheduled for a surgical procedure, but unfortunately she expired at home during her sleep a week later. Examination of the brain confirmed the hemi‐atrophy of the right cerebral hemisphere and left cerebellum. Microscopic examination showed severe gliosis and perivascular lymphocytic infiltrates in many areas. A diagnosis of Rasmussen's encephalitis was made. Rasmussen's encephalitis is a chronic neurological disorder, first described in 1958. The active neurological decline lasts from 1 to 20 years and the patients then remain stable with a fixed neurological deficit and residual seizures. Pathological examination shows a chronic encephalitis confined to one hemisphere. In the active phase, neuronophagia, activated microglial cells (rod cells), microglial nodules, and perivascular lymphocytic infiltrates, are present. In the more chronic phase neuronal loss and gliosis predominate. The etiology of Rasmussen's encephalitis is unknown but viral infection and autoimmunity have been implicated. The treatment of choice is functionally complete hemispherectomy with complete disconnection of the frontal and occipital lobes The November 2002 COM. A 72‐year‐old immunocompetent woman presented with recent confusion, memory loss, visual and a gait disturbance. MRI scans demonstrated a T2 hypointense, gadolinium enhancing mass in her pineal region. A whole body CT scan identified a large retroperitoneal mass and significant lymphadenopathy. She underwent a biopsy of the pineal lesion. The intraoperative smear contained discohesive, basophilic malignant cells of moderate size that had only scant cytoplasm, an increased nuclear‐to‐cytoplasmic ratio and irregular, hyperchromatic nuclei containing prominent nucleoli. Mitotic figures, apoptotic and lymphoglandular bodies were frequent. Histologic examination showed malignant cells infiltrating and almost completely replacing the residual pineal gland. The tumor cells immunoreacted with LCA and CD‐20. Scattered CD3 and UCHL‐1 positive cells were also present. The diagnosis was stage IV, high grade, large B‐cell lymphoma involving the pineal gland and retroperitoneum. Four cycles of systemic chemotherapy significantly reduced the patient's retroperitoneal mass. However, a repeat head MRI scan continued to show gadolinium‐enhancement in the pineal region, now with extension into contiguous brain parenchyma and the subependymal region. The patient died 4 months after presentation. At autopsy, the lymphoma encased the pineal region and disseminated along the ventricular walls and into the subarachnoid spread. Pineal‐region tumors are rare in the elderly population, and although unusual, lymphomas should be considered in this context. The behavior of this circumventricular organ lymphoma was comparable to both peripheral and primary central nervous system lymphomas. The December 2002 COM. A 19‐year‐old healthy male fell into stagnant water of the intercostal waterway (salt water of South Florida), following a jet ski accident. He sustained minor superficial injuries but engulfed significant quantities of water and sediment. A few days later he developed bifrontal headaches, vomiting, a stiff neck and a temperature of 102°F. A CT scan on admission without contrast was negative. The CSF had markedly elevated white count but bacterial and fungal cultures were negative. He became progressively lethargic. On the fifth day he developed seizure activity. He expired the next day despite antibiotics. Gross examination of the brain at autopsy revealed edema, cerebellar tonsillar herniation and purulent meningitis. Microscopic examination revealed a massive leptomeningeal inflammatory infiltrate composed of neutrophils, lymphocytes, and numerous histiocyte‐like cells. The inflammatory infiltrate extended into the cerebral parenchyma in numerous areas also involving the cerebellum, brainstem and ventricular system. Given the exposure to stagnant water (later confirmed to be a man‐made fresh water lake), and the numerous histiocytic‐like cells, suspicion for an amebic etiology of the disease process was raised and the CDC identified the ameba as Naegleria Fowleri. Infection by Naegleria Fowleri, a free‐living ameba, occurs after exposure to polluted water in man‐made fresh water lakes, ponds, swimming pools, particularly during the warm weather months when the thermophilic ameba grows well. The pathologic substrate of the infection is an acute hemorrhagic, necrotizing meningo‐encephalitis mainly at the base of the brain, brainstem and cerebellum occurring in young, healthy individuals.