Brain single-photon emission computed tomography.

Single-photon emission computed tomography (SPECT) provides cost-effective information on regional cerebral perfusion and, indirectly, on regional cerebral metabolism. Its ease of use facilitates the application of SPECT in clinical neurology. SPECT is emerging as a useful tool for the management of patients with stroke, epilepsy, recurrent brain neoplasms, and some forms of dementia. The applications being investigated, such as in vivo receptor labeling for benzodiazepines, serotonin, dopamine, and muscarinic receptors, may expand the clinical usefulness of this technique in the future.

Ocular thrombosis associated with antiphospholipid antibodies.

Four patients with isolated acute ocular ischemic syndromes also had circulating antiphospholipid antibodies. Two patients had vaso-occlusive retinopathy and two, anterior ischemic optic neuropathy (which was successive in one). Extensive clinical laboratory evaluation identified vascular risk factors in two patients. One patient had essential thrombocytosis, confirmed by bone marrow biopsy; the other had stable hypertension and a history of coronary artery disease. These cases suggest that small vessel thrombosis in situ may be a mechanism for antiphospholipid-associated ocular and cerebral ischemia.

Transcranial Doppler in acute hemispheric brain infarction.

We studied cerebrovascular anatomy using intra-arterial digital angiography, and blood flow velocity in the middle cerebral artery (MCA) using transcranial Doppler (TCD) ultrasonography in 42 patients with acute hemispheric ischemic brain infarction. We compared angiography with TCD and the clinical findings within 6 hours of the onset of symptoms. The location and extent of the chronic ischemic brain damage was assessed by CT performed 1 to 3 months after the ictus. Abnormal TCD, as manifested by either an unobtainable MCA flow signal or a significantly depressed MCA flow velocity, was highly associated with proximal MCA occlusions demonstrated by angiography. Abnormal TCD predicted both larger chronic CT lesions and more extensive ischemic change within the MCA territory. These data demonstrate that early TCD conveys useful information concerning cerebral tissue prognosis following hemispheric ischemia.

Prospective study of anticardiolipin antibodies in stroke.

Over 2 years, 104 patients underwent clinical evaluation and laboratory screening for the presence of abnormal anticardiolipin antibodies to determine the profile of laboratory and clinical findings in patients with stroke and other neurologic disorders. Seven with incomplete or ambiguous data were excluded; of the remaining 97 patients, 31 were greater than or equal to 65 years old. Nine patients suffered systemic lupus erythematosus, 45 suffered brain ischemia, and 43 suffered other nonischemic neurologic disorders. Cardiac arrhythmia, myocardial infarction, and cardiac valvulopathy were grounds for exclusion. The presence of anticardiolipin antibodies was not influenced by age. In the 88 patients without lupus, anticardiolipin antibodies were significantly more common in the group suffering brain ischemia than in the group with nonischemic neurologic disorders (29% versus 5%, p less than 0.01, chi 2 test). These controlled data demonstrate an association between the presence of circulating anticardiolipin antibodies with stroke, but not with other neurologic conditions.

Cerebral blood flow variations in CNS lupus.

We studied the patterns of cerebral blood flow (CBF), over time, in patients with systemic lupus erythematosus and varying neurologic manifestations including headache, stroke, psychosis, and encephalopathy. For 20 paired xenon-133 CBF measurements, CBF was normal during CNS remissions, regardless of the symptoms. CBF was significantly depressed during CNS exacerbations. The magnitude of change in CBF varied with the neurologic syndrome. CBF was least affected in patients with nonspecific symptoms such as headache or malaise, whereas patients with encephalopathy or psychosis exhibited the greatest reductions in CBF. In 1 patient with affective psychosis, without clinical or CT evidence of cerebral ischemia, serial SPECT studies showed resolution of multifocal cerebral perfusion defects which paralleled clinical recovery.

Atherosclerotic carotid artery disease in patients with retinal ischemic syndromes.

The extracranial carotid systems of 105 patients with retinal ischemia were examined using B-mode ultrasonography with integrated pulsed Doppler. Sixty-four patients had amaurosis fugax (AF), 17 central retinal artery occlusions (CRAO), and 21 branch retinal artery occlusions (BRAO). The prevalence of carotid stenosis (greater than or equal to 60%) ipsilateral to the symptomatic eye was low (16%). Eighty-six percent of AF patients had either no plaque causing less than a 60% stenosis. A significant proportion of subjects with normal duplex scans had alternative explanations for their retinal ischemia (eg, migraine, cardiac embolus). Patients with Hollenhorst plaques were more likely to have stenotic or ulcerated plaque (p = 0.04). The degree of carotid stenosis correlated significantly with the number of vascular risk factors identified in individual patients (p = 0.02). The presence of risk factors was more common in CRAO and BRAO patients compared with the AF group. Combined ultrasound-Doppler investigations of the carotid bifurcation are valuable noninvasive tools for the screening of patients with retinal ischemia.

Cerebral metabolism and patterned visual stimulation: a positron emission tomographic study of the human visual cortex.

We studied the impact of visual stimulation upon cerebral metabolism in normal young men using FDG-PET. Results obtained from subjects receiving patterned visual stimulation while performing an ocular fixation task were compared with results from ocular fixation alone. Visual stimulation in the macular region of either hemifield produced significant increases in metabolism of the contralateral posterior striate cortex. Visual stimulation induced highly significant asymmetries in metabolism of the prefrontal and inferior parietal cortices. Metabolic activation in extrastriate areas tended to be right-sided. These findings support the classic notion of retinotopic organization within the primary visual sensory cortex. They also indicate that the patterns of cerebral metabolism are not equivalent between the two cerebral hemispheres. This latter finding suggests that in humans the right cerebral hemisphere may be specialized for visual processing.

Cerebral blood flow in systemic lupus erythematosus with or without cerebral complications.

We measured mean cerebral blood flow (CBF) in 25 lupus patients using the xenon-133 method. The CBF was normal in lupus patients without cerebral disease and also in CNS lupus patients in remission. The CBF was lower than normal during bouts of cerebral lupus (p less than 0.001). Repeat studies showed a stereotyped pattern consisting of depressed CBF during exacerbation of CNS disease and normalization of CBF during remission (p less than 0.01). These results show that CBF is a sensitive indicator of activity of CNS disease and that the direction of change in CBF reflects the clinical course of CNS lupus.

Positron emission tomography in aging and dementia: effect of cerebral atrophy.

The spatial resolution of current positron emission tomography (PET) scanners does not allow a distinction between cerebrospinal fluid (CSF) containing spaces and contiguous brain tissue. Data analysis strategies which therefore purport to quantify cerebral metabolism per unit mass brain tissue are in fact measuring a value which may be artifactually reduced due to contamination by CSF. We studied cerebral glucose metabolism (CMRglc) in 17 healthy elderly individuals and 24 patients with Alzheimer's dementia using [18F]fluorodeoxyglucose and PET. All subjects underwent x-ray computed tomography (XCT) scanning at the time of their PET study. The XCT scans were analyzed volumetrically, in order to determine relative areas for ventricles, sulci, and brain tissue. Global CMRglc was calculated before and after correction for contamination by CSF (cerebral atrophy). A greater increase in global CMRglc after atrophy correction was seen in demented individuals compared with elderly controls (16.9% versus 9.0%, p less than 0.0005). Additional preliminary data suggest that volumetric analysis of proton-NMR images may prove superior to analysis of XCT data in quantifying the degree of atrophy. Appropriate corrections for atrophy should be employed if current PET scanners are to accurately measure actual brain tissue metabolism in various pathologic states.

Cerebral glucose consumption following verbal auditory stimulation.

We studied the effect of auditory stimulation upon cerebral glucose metabolism in young normals. The stimulus consisted of a non-English discourse which was presented monaurally to 10 normal blindfolded subjects (5 left ear, 5 right); the opposite ear was plugged. Six subjects studied blindfolded and with ears plugged served as controls. Sixteen discrete homologous cortical and subcortical regions of interest were examined. Regional glucose consumption and side-to-side differences in glucose metabolism were analyzed. Monaural stimulation produced significant increases in temporal metabolism contralateral to the side of stimulation. Significant asymmetries in metabolism were found at the temporoparietal junction, inferior parietal region, insula and corpus collosum. The left frontal speech areas remained unaffected. These findings demonstrate that in man the primary auditory pathways retain a contralateral organization. Further, cerebral activation induced by non-meaningful verbal stimulation is widespread within the left temporal and parietal regions but does not impact upon the frontal speech cortices.

Stimulated Brillouin scattering parasitics in large optical windows.

The growth of optical radiation, scattered transverse to the pump axis by stimulated Brillouin scattering (SBS) in optical windows, is considered. Basic equations are presented, and an analytic expression that determines the parasitic buildup time is derived for a transverse SBS geometry. Losses suffered by the scattered optical radiation are included in a bulk-loss term. Calculations are performed for fused-silica windows and compared with a numerical model. This parasitic process may affect the design of laser systems that will generate multinanosecond, multikilojoule, narrow-band pulses in the ultraviolet region.

Comparison of two transdermal nitroglycerin systems.

In a study conducted by office-based cardiologists at eight sites, 115 patients using transdermal nitroglycerin for treatment of angina pectoris participated in a four-week comparison of two transdermal nitroglycerin patches: Transderm-Nitro (TDN) and Nitro-Dur II (ND II). Patients wore two patches, one of each brand, each with half their normal prescribed daily dose of 10 mg (release rate per 24 hours) to compare patch adherence properties, patient preference, and local side effects. More ND II than TDN patches fell off (5% versus 0.1%), and fewer TDN than ND II patches became loose (1.7% versus 8.4%); 98.2% of the TDN and 86.7% of the ND II patches adhered totally. Significantly more patients expressed a preference for TDN over ND II in four of eight assessment variables, including the choice of their next prescription. The frequency of problems at the site of patch application was similar with both patches.

Transient global amnesia: a case-control study.

The clinical findings and laboratory results from 18 patients with clear-cut transient global amnesia (TGA) were compared with the results from 90 nonischemic neurological control patients using case-control analysis. A prior episode of cerebral ischemia, generally in the posterior circulation, was the most significant risk factor for TGA. Other risk factors for cerebrovascular disease were more prominent in the TGA group, but this association became less significant when cerebral ischemia was controlled for. Migraine, epilepsy, and psychiatric disorders were not significantly associated with TGA. In 5 of 13 patients, computed tomography showed focal thalamic and temporal lobe abnormalities. The recurrence rate was 7.0% for both TGA and subsequent cerebral ischemia. We conclude that TGA is closely linked to cerebrovascular disease. Further, prior damage to anatomical structures critical to memory may be necessary for the expression of this syndrome.

The clinical manifestations of pontine hemorrhage.

The survival rate was 40% in 10 patients suffering hemorrhage into the pons who were admitted to an acute care facility. This rate is higher than previously reported. In addition to the "classic" pontine hematoma syndrome characterized by coma, quadriparesis, and eventual demise, two more benign syndromes arising from hemorrhage confined to one side of the pons were also recognized. In one of these hemipontine syndromes, hematoma involved both the basis pontis and tegmentum and was associated with hemiparesis, brainstem signs, and preserved consciousness. In the other, hemorrhage was confined to the tegmentum and was associated with gaze paresis, motor sparing, and preserved consciousness. All patients suffering hemipontine hemorrhage survived. An impressive degree of functional recovery occurred in these survivors.

Nystagmus in motor neuron disease: clinicopathological study of two cases.

Two patients with amyotrophic lateral sclerosis proved postmortem had nystagmus in addition to typical clinical signs of motor neuron disease. The first patient had gaze-evoked rotatory nystagmus that was followed by horizontal nystagmus in the primary position with supranuclear paresis of horizontal gaze and upgaze. The second patient had rotatory nystagmus that was evoked by lateral gaze, with normal range of eye movements. Nystagmus is so rare in motor neuron disease that these observations may imply another disease, but postmortem examination did not provide any other explanation. These two cases add to the increasing evidence that motor neuron disease comprises a heterogeneous group of disorders.

Posterior fossa epidural hematoma. A report of three cases diagnosed with computed tomography.

CT demonstrated posterior fossa epidural hematoma in three patients with head trauma in whom this diagnosis was not clinically apparent. No patient was in stupor or coma and no patient experienced a lucid interval. Only one patient had signs referable to the posterior fossa. Two patients had occipital skull fracture disclosed by plain radiographs. CT revealed a unilateral biconvex hematoma in two cases, and a bilateral hematoma with supratentorial extension in the third. All patients underwent suboccipital craniectomy and recovered. Therapeutic success in these cases was facilitated by early CT and the rapid disclosure of the unsuspected posterior fossa lesions. CT showing contiguous hematoma below and above the tentorium cerebelli after posterior head trauma is highly suggestive of epidural hematoma arising from the posterior fossa.