B S Brooks

Frequency and variation of the posterior pituitary bright signal on MR images

Sagittal T1-weighted series with 3-mm sections have routinely been used for all cranial MR studies at our institution. It was apparent from examining these studies that the rate of occurrence of a normal posterior pituitary bright signal was lower than has been previously reported, particularly in older patients. This prompted both a retrospective and a prospective review and analysis of the posterior lobe bright signal in three patient categories. The overall frequency of posterior pituitary bright signal and the influence of sex and age were evaluated in one category. An age-related statistically significant decline in the frequency of posterior pituitary bright signal was found, with a decline rate of approximately 1% per year. An evaluation of the occurrence of anatomic variation in the location of posterior lobe bright signal was made in a second group of 1500 patients. Abberrant location of the posterior lobe was found to be uncommon and was seen most frequently in patients with a sellar fossula. Temporal variation in the presence or absence and size of the posterior lobe bright signal was evaluated in a third group of 36 patients who had at least two MR examinations available for review. Follow-up MR study showed an obvious posterior lobe bright signal in 8% of these patients for whom no bright signal was apparent at the time of initial examination. Loss of the posterior lobe bright signal was apparent in another 25% of patients. A significant change in size of the bright signal was apparent in 19% of patients within this category. Our results indicate that variation in the bright signal of the posterior pituitary lobe should be expected as a normal physiological occurrence.

Severe behavioral complications following intracarotid sodium amobarbital injection: implications for hemispheric asymmetry of emotion

The intracarotid sodium amobarbital (ISA) procedure is effective in determining cerebral language dominance. However, severe emotional and behavioral reactions during ISA evaluation may invalidate the results or necessitate aborting the procedure. In an effort to identify patients at risk for behavioral complications, we reviewed 92 patients undergoing ISA evaluation and found five with severe changes in affect and behavior following amobarbital injection, ranging from prolonged coma to an extended confusional state. Severe behavioral disturbances were more likely to occur in patients with left frontal structural lesions upon injecting amobarbital into the right hemisphere. Analysis of patients with structural lesions of the anterior regions of the right hemisphere showed no evidence of similar behavioral complications. These findings suggest a special role for the left frontal region in the inhibition of affective expression and provide further evidence of the importance of right hemisphere mechanisms in emotion.

Right cerebral specialization for tactile attention as evidenced by intracarotid sodium amytal.

Although several components of neglect syndrome have been reported to occur more frequently following right cerebral lesions, a right cerebral predominance for directed tactile attention has not been demonstrated. The intracarotid sodium amytal procedure (ISA, or Wada test) offers the opportunity to investigate differential effects for symmetric acute dysfunction of each cerebral hemisphere in each subject. In the present study, 18 patients undergoing preoperative evaluation for epilepsy surgery were trained in a nonverbal task of tactile attention. Left/right mean ISA dosages and left/right tactile test times postinjection were matched. Results revealed more correct responses following left ISA, and greater tactile inattention with more extinction-type responses following right ISA. No effect of seizure focus, sex, order of injection, or dosage was present. The finding that tactile inattention occurs more frequently with right cerebral dysfunction is consistent with right cerebral dominance for scanning attentional mechanisms directed at the external milieu.

Attentional mechanisms during the intracarotid amobarbital test

We investigated the integrity of attentional mechanisms following unilateral intracarotid amobarbital injection in 23 patients undergoing preoperative evaluation for epilepsy surgery. Performance for ipsilateral hand-button response to a quasi-random strobe flash was markedly altered following unilateral amobarbital injection as evidenced by decreased correct responses and increased perseverative errors. The increase in perseverations was inversely correlated with subsequent memory performance. The results indicate that unilateral amobarbital injection commonly produces a marked reduction in attention as well as disturbances in strategic control mechanisms.

Giant posterior inferior cerebellar artery aneurysm with dysphagia

Presented is a case of giant aneurysm of the posterior inferior cerebellar artery with the unusual clinical presentation of dysphagia to the point of inability to swallow even oral secretions, resulting in severe malnutrition. A computed tomography scan with contrast-medium enhancement appeared normal. The correct diagnosis was suspected from the results of metrizamide myelocisternography and was confirmed at angiography. The patient underwent ligation of the feeding right vertebral artery with subsequent improvement in her dysphagia and resolution of her other neurological deficits. Discussion of the incidence, diagnosis, and treatment of this uncommon lesion is presented.

Ventriculoperitoneal shunt metastasis of a pineal germinoma

Metastasis of pineal germinoma to the peritoneal cavity via the patients ventriculoperitoneal shunt represents an unusual complication of this rare tumor. We report such a case with autopsy correlation of the abdominal CT findings. CT accurately delineated the extent of the metastatic mass and revealed associated complications including biliary tract obstruction, thrombosis of the inferior vena cava and a small amount of ascitic fluid. Since this tumor is very sensitive to radiotherapy and chemotherapy, the need for early detection of such metastasis is apparent. Possible implications with respect to the management of these patients are considered.

Cerebellar atrophy in epilepsy and headache Lack of relationship to phenytoin

CT scans of 70 patients with seizures and 48 patients with headaches were studied. Using accepted CT criteria for the diagnosis of cerebellar atrophy, the films were analyzed in a blind, unbiased fashion to evaluate possible relationship between cerebellar atrophy and phenytoin use or epilepsy itself. We found no evidence that either phenytoin or epilepsy caused cerebellar atrophy.

Hematogenous spinal leptomeningeal metastasis: a unique CT enhancement pattern

A distinct CT enhancement pattern of leptomeningeal metastasis from a systemic malignancy is described, corresponding to the pathologic and myelographic patterns of this entity. The uniform total subarachnoid enhancement, simulating intrathecal contrast, heralded sheetlike tumor proliferation along the surface of the spinal cord in an asymptomatic patient. Since the majority of hypervascular intraspinal abnormalities show focal enhancement with intravenous contrast, recognition of this pattern may provide unique clinical information.