Parieto-cerebellar loop impairment in ataxic hemiparesis: proposed pathophysiology based on an analysis of cerebral blood flow

Diffusion weighted imaging in ataxic hemiparesis

OBJECTIVE

Ataxic hemiparesis (AH) is a well recognised lacunar syndrome involving homolateral ataxia with accompanying corticospinal tract impairment. Most previous studies of lesion location in AH did not use diffusion weighted MRI (DW MRI). The purpose of this study was to use DW MRI to evaluate the radiological correlation in patients presenting with AH.

METHODS

Retrospectively, we studied 29 patients with AH using DW MRI.

RESULTS

All patients were scanned within 4 days of onset. Acute infarction was identified in 28 of 29 (97%) patients. A single lesion was identified in 26

PATIENTS

pons (n = 8), internal capsule (n = 6), corona radiata (n = 2), distended internal capsule from corona radiate (n = 7), frontal subcortical area (n = 1) and precentral with or without postcentral gyrus (n = 2). Two lesions were found in two patients: in the pons and corpus callosum of one patient, and in the corona radiata and subcortical white matter of the other.

CONCLUSIONS

AH is mainly caused by pontine or internal capsule/corona radiata lesions. It also occurs in the precentral gyrus, including the precentral knob, with or without postcentral gyrus lesions. Fibres of the fronto-ponto-cerebellar system may originate from the frontal cortex, including the precentral gyrus, probably near the pyramidal tract. Damage at this location may cause AH.

Cerebral and cerebellar diaschisis following carbamazepine therapy

1. The regional cerebral blood flow was studied by SPECT in patients with partial epilepsy before and after 30 days of monotherapy with carbamazepine (CBZ). 2. Both a qualitative visual interpretation and a semiquantitative analysis of SPECT was performed. All patients underwent EEG, CT scan, and MRI studies. The CBZ serum concentrations were assayed. 3. After therapy, in three patients with focal epilepsy, both a crossed cerebral and cerebellar diaschisis were observed, with respect to the side of the epileptic focus in the opposite hemisphere. No morphologic changes were detected at MRI in the cerebral or cerebellar remote hypometabolic areas found at SPECT. 4. CBZ may have a depressant action on the corticopontocerebellar pathways and on the corticocallosal connections.