Paraneoplastic myelitis with involvement of the dorsal columns. MRI findings and differential diagnosis

Paraneoplastic syndroms of the central nervous system may precede the clinical presentation of a tumor by years. An early diagnosis may improve the prognosis of the underlying disease. We report clinical and imaging signs of a patient presenting with paraneoplastic poly-neuropathy and myelitis, 18 months before the diagnosis of a small anaplastic breast carcinoma could be made. Spinal MRI showed primarily involvement of the dorsal columns, thought to be suggestive of a subacute combined degeneration due to vitamin B12 deficiency

Complete agenesis of the corpus callosum but persistant hippocampal commissure: Differential diagnostic criteria

Agenesis of the corpus callosum is mostly observed in the context of maldevelopmental syndromes and associated with further structural abnormalities. The callosal defect may be partial or complete. Other than the absence of the corpus callosum itself, indirect criteria may help in the identification of callosal malformations. We report on a patient with complete callosal agenesis, who had a persistant hippocampal commissure. This fiber tract may cause diagnostic difficulties but can reliably be identified if the morphology of the hippocampus and the indirect signs of callosal agenesis are taken into consideration

Detection of acute thalamo-mesencephalic infarction: diffusion abnormality precedes T2 hyperintensity.

OBJECTIVE: To examine the time course of signal changes in diffusion-weighted magnetic resonance imaging (DW-MRI) and T2-weighted MRI in a case of cerebral infarction in the posterior circulation territory. MATERIALS AND METHODS: Diffusion- and T2-weighted MRI and comparison of signal changes in these sequences at 4 h, 1 day and 4 days after the onset of clinical symptoms caused by acute thalamo-mesencephalic infarction. RESULTS: Four hours after the onset of symptoms, signal changes in DW-MRI revealed an infarction in the territory of the posterior perforating thalamic artery, whereas no signal changes were detected in T2-weighted MRI. In follow-up MRI 1 and 4 days after infarction, however, a marked hyperintensity matching the location of the diffusion deficit could be identified in T2 images. CONCLUSION: Signal changes in DW-MRI precede T2 hyperintensity after infarction in the posterior circulation territory after hemispheric infarction

MRI features of primary, secondary and metastatic medulloblastoma.

Medulloblastoma is the most frequent paediatric malignant brain tumour. The purpose of this study was to define imaging characteristics and contrast uptake patterns of primary and recurrent medulloblastoma using MRI. The MRI examinations of 17 histologically proven cases of medulloblastoma diagnosed in our institution (13 males and 4 females; mean age 13 years, 7 months) were reviewed in retrospect. Only patients with pre-treatment and follow-up examinations including T2-weighted images (fluid-attenuated inversion recovery or turbo spin echo) and T1-weighted images after contrast injection (0.1 mmol/kg Gd-DTPA) were included in this study. Whereas 6 of 7 tumours ( n=17) were hyperintense on T2-weighted images, contrast enhancement was detected in 13 patients. Fifteen tumours occurred in the cerebellar vermis, two were located in the cerebellar hemispheres. Mean size at the time of presentation was 30.1 mm. All patients presented with some extent of an occlusive hydrocephalus. Local recurrent tumour or metastases were seen in 6 patients (3 months to 7 years, mean age 2.5 years). Whereas the T2 signal intensity of recurrent tumour or subarachnoidal metastases resembled the primary neoplasms, the contrast uptake tended to be less pronounced ( n=3) or was completely absent ( n=2); thus, suggestive signs of primary medulloblastoma are location in the vermis, hyperintensity on T2-weighted images and hydrocephalus. The amount of contrast enhancement is variable and nonspecific. Secondary medulloblastoma manifestation is characterized by T2 hyperintensity but not by contrast uptake