The dynamic signal intensity changes at magnetic resonance (MR) imaging in active and chronic wallerian degeneration in the corticospinal tract were evaluated. Forty-three patients with wallerian degeneration seen on MR images after cerebral infarction were studied. When possible, patients with acute stroke were examined with MR imaging prospectively at the onset of symptoms and then at weekly intervals for several months. Focal infarction without distal axonal degeneration is demonstrated for the 1st month following onset of clinical symptoms. At 4 weeks, a well-defined band of hypointense signal appears on T2-weighted images in the topographic distribution of the corticospinal tract. After 10-14 weeks, the signal becomes permanently hyperintense. Over several years, accompanying ipsilateral brain stem shrinkage occurs. The dark signal intensity observed on T2-weighted images between 4 and 14 weeks is believed to result primarily from transitory increased lipid-protein ratio.

The authors investigated whether identification of corpus callosal (CC) involvement might increase the specificity of magnetic resonance (MR) imaging in differentiating multiple sclerosis (MS) from other periventricular white matter diseases (PWDs). They prospectively evaluated 42 patients with MS and 127 control patients with other PWDs. Ninety-three percent of the MS patients demonstrated confluent and/or focal lesions involving the callosal-septal interface (CSI). These lesions characteristically involved the inferior aspect of the callosum and radiated from the ventricular surface into the overlying callosum. CSI lesions were optimally demonstrated on sagittal long repetition time (TR)/short echo time (TE) images and frequently (45% of cases) went undetected on axial images. Only 2.4% of the control patients had lesions of the CC. The authors conclude that midsagittal long TR/short TE images are highly sensitive and specific for MS and that callosal involvement in MS is more common than previously reported.

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Twenty-three patients who underwent routine magnetic resonance (MR) imaging of the brain were found to have signal or structural abnormalities corresponding to white matter tracts. Images were evaluated for anatomic and MR signal characteristics of the involved tract, associated primary lesions, and, when possible, changes in MR signal and anatomic structures with time. Images from 20 patients demonstrated a thin band of abnormal signal contiguous with the primary lesion and conforming to the known anatomic pathway of a white matter tract. Cerebral infarction was the most common associated primary disorder (n = 17). Neoplasms (n = 2), demyelinating (n = 1) and posthemorrhagic (n = 2) conditions, and an idiopathic movement disorder (n = 1) were associated with white matter tract signal abnormalities that were indistinguishable from those seen with infarction. Signal abnormality corresponding to the corticospinal tract was the type most commonly seen. No change in signal characteristics was seen with time (six cases) or following contrast material administration (two cases). The authors conclude that MR imaging provides a sensitive method of evaluating wallerian degeneration in the living human brain.

Fifteen patients with biochemically documented phenylketonuria (PKU) were studied with use of magnetic resonance (MR) imaging with spin-echo T2-weighted pulse sequences. The resulting images demonstrated varying degrees of symmetric high signal intensity of the white matter within the posterior cerebral hemispheres. Involvement of the anterior hemispheres was seen only in cases with severe signal intensity changes. There was no involvement of the cerebral cortex, brain stem, or cerebellum. Moreover, no anatomic structural abnormalities were observed. Mild cortical atrophy was observed in eight of the 15 patients. There was no significant correlation between the patients' IQ scores and the level of MR signal intensity changes. Although MR imaging routinely shows relatively distinct abnormalities in patients with PKU, the clinical severity of the disease does not parallel its imaging severity.

SUMMARY We retrospectively reviewed the dinkal course and angiograms of 15 patients with carotid siphon stenosis of 50% or greater. Fourteen had less than 50% stenosis at the origin of the ipsilateral internal carotid artery, and one had a greater degree of stenosis but underwent endarterectomy after an initial angiogram. Angiograms were examined for evidence of hemodynamk abnormalities in addition to residual lumen diameter. Seven patients initially had TIAs, 5 had strokes, and 3 were asymptomatic. In an average followup of 51 months (range 4-123 months) subsequent cerebral ischemic events occurred in 6 (40%), but only 1 had a stroke with a persisting neurological deficit that could be directly attributed to the siphon stenosis. Stenoses were hemodynamically significant by angiography in 5 of 7 TIA patients, and only 1 of 5 stroke patients. The incidence of subsequent ischemic events in this study was similar to 2 previous studies of siphon stenosis, however hi this study most of the events ipsilateral to the siphon stenosis were TIAs or minor strokes. The association of hemodynamk angiographic abnormalities and initial TIAs but not strokes suggests that the mechanism producing ischemic symptoms may differ in patients with TIA and stroke who have carotid siphon stenosis. Stroke Vol 17, No 4, 1986 CALCIFICATION of the carotid siphon or intracranial internal carotid artery occurs frequently, but significant stenosis of this segment is less common.' Stenosis of the carotid siphon has been estimated to be about one-sixth as common as disease of the carotid bifurcation.2 Until recently, little was known about the natural history of stenosis of the carotid siphon. Two previous studies of siphon stenosis found that 30-^40% of such patients had subsequent ischemic events, and more than half of these events were ipsilateral to the siphon stenosis.3 ' 4 Clinical details of events occurring during followup were limited in both studies, and the angiographic data included only the site and severity of stenosis. Angiograms were not examined for collateral flow or hemodynamic significance of the siphon stenosis.We therefore retrospectively reviewed clinical and angiographic information on 15 patients with carotid siphon stenosis of 50% or greater. Fourteen had less than 50% stenosis of the ipsilateral extracranial carotid and 1 had severe ipsilateral extracranial stenosis but underwent endarterectomy shortly after angiography. All angiograms were reviewed for hemodynamic as well as anatomic information and the results were correlated with the nature of initial and subsequent ischemic events. MethodsPatients were identified by reviewing the angiography records of the neuroradiology department for the past 5 years for the diagnosis of stenosis of the carotid siphon. Those with greater than 50% stenosis of the ipsilateral extracranial internal carotid artery, ipsilateral carotid occlusion, or middle cerebral artery stenosis were excluded unless carotid endarterectomy was performed after angiography. The medical records were t...

An analysis has been made of the clinical manifestations in 18 cases of hypertensive thalamic hemorrhage diagnosed by computed tomography (CT). CT scans permitted accurate determination of the site, size, and extension of the hemorrhages. A sensorimotor hemiplegia or hemiparesis was present in all cases. Diagnostic clinical features included limitation of vertical gaze, downward deviation of the eyes, and small unreactive or sluggish pupils. All hemorrhages larger than 3.3 cm in diameter were fatal.

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