Morphometry of in vivo human white matter association pathways with diffusion-weighted magnetic resonance imaging.

The precise characterization of cortical connectivity is important for the understanding of brain morphological and functional organization. Such connectivity is conveyed by specific pathways or tracts in the white matter. Diffusion-weighted magnetic resonance imaging detects the diffusivity of water molecules in three dimensions. Diffusivity is anisotropic in oriented tissues such as fiber tracts. In the present study, we used this method to map (in terms of orientation, location, and size) the "stem" (compact portion) of the principal association, projection, and commissural white matter pathways of the human brain in vivo, in 3 normal subjects. In addition, its use in clinical neurology is illustrated in a patient with left inferior parietal lobule embolic infarction in whom a significant reduction in relative size of the stem of the left superior longitudinal fasciculus was observed. This represents an important method for the characterization of major association pathways in the living human that are not discernible by conventional magnetic resonance imaging. In the clinical domain, this method will have a potential impact on the understanding of the diseases that involve white matter such as stroke, multiple sclerosis, amyotrophic lateral sclerosis, head injury, and spinal cord injury.

The clinical spectrum of cerebral amyloid angiopathy: presentations without lobar hemorrhage.

Cerebral amyloid angiopathy is a common cause of spontaneous lobar hemorrhage in elderly patients. We discuss seven patients with amyloid angiopathy presenting without major lobar hemorrhage. The patients' presentations fell into two groups: recurrent transient neurologic symptoms and rapidly progressive dementia. The cases with transient episodes had a spread of symptoms to contiguous body areas during episodes. Each had evidence of small hemorrhage or subsequent large hemorrhage in the cortical location corresponding to the symptoms, suggesting petechial hemorrhage with focal seizure as the cause of the transient spells. Three cases of dementia developed with relatively rapid time courses, progressing from intact baseline to profound dementia in spans of a few days to 2 years. Pathologic abnormalities, in addition to amyloid angiopathy, included patchy white matter demyelination and tissue loss, petechial cortical hemorrhages, cortical infarctions, and a variable degree of neuritic plaques and neurofibrillary tangles. The clinical spectrum of cerebral amyloid angiopathy includes these two neurologic syndromes.

Sleep EEG in bulimia.

To evaluate the sleep electroencephalogram (EEG) characteristics of bulimia, all-night sleep EEGs were performed on 11 women meeting DSM-III criteria for bulimia. Comparison groups consisted of young women outpatients with major depression (n = 44) and young normal women (n = 20). The sleep EEGs of the bulimic patients were largely indistinguishable from those of the normal controls, except for a trend toward increased rapid eye movement (REM) density in the first REM period among the bulimic subjects. No differences in any sleep EEG measure were observed between bulimic patients with major depression and those without affective disorder. By contrast, the outpatients with major depression displayed marked sleep continuity disturbances, as well as significantly increased REM intensity and REM density, as compared to normal controls. Implications of these results with respect to the hypothesis that bulimia is related to major affective disorder are discussed.

Periodic leg movements of sleep (nocturnal myoclonus): an electrophysiological study.

Six patients with periodic leg movements of sleep (PLMS) were studied electrophysiologically. All patients had normal results on routine nerve conduction studies and electromyography. In 5 patients the blink reflex consisted of three components, and in 1 patient it consisted of four components, with two components being normal. The second component of their blink reflex did not habituate. Other abnormalities included long-latency responses in the extremities in 2 patients, release of H-reflexes from flexor hallucis brevis muscle in 2 patients, and an Hmax/Mmax ratio of 98% in 2 patients. One patient's median nerve somatosensory-evoked response had a markedly enlarged P22 wave. These electrophysiological abnormalities suggest a disorder of the central nervous system producing increased excitability of segmental reflexes. To produce increased excitability of both brainstem and spinal cord reflexes, the disorder must be operative at the pontine level or rostral to it. Since long-latency components of blink reflexes occurred in all our patients, this may be a helpful diagnostic test when PLMS is suspected.

Reversible alteration of the visual evoked potential in hypothyroidism.

The pattern-shift evoked potential was measured in 19 hypothyroid patients before treatment, and after short- (one week) and long-term (12 to 24 weeks) thyroid hormone replacement therapy. Before treatment, nine patients had an abnormally prolonged visual evoked potential latency, more than 115 msec. After one week of therapy with 50 micrograms per day of L-triiodothyronine, the mean visual evoked potential latency for the entire group was unchanged, 114 +/- 8 to 114 +/- 7 msec. However, long-term therapy with 100 to 200 micrograms per day of L-thyroxine significantly shortened the visual evoked potential latency to 105 +/- 1 msec (p less than 0.001). In eight of the nine patients with initially abnormal results, the visual evoked potential latency was completely restored to normal. The visual evoked potential amplitude was also significantly changed by long-term L-thyroxine, 4.8 +/- 0.7 to 9.0 +/- 1.0 microV (p less than 0.01). It is concluded that the visual evoked potential is reversibly altered in hypothyroidism. This neurophysiologic parameter permits quantitation of the effects of hypothyroidism on the central nervous system and the extent and rate of response to thyroid hormone replacement therapy.

Transient cataplexy after removal of a craniopharyngioma.

We studied a patient with cataplexy secondary to a surgical lesion that involved the perichiasmal hypothalamus. We believe that this lesion interfered with the hypothalamic mechanism for timing sleep and wakefulness, whereas the pontine mechanism for generating sleep cycles remained relatively intact.