Parietal ataxic hemiparesis

Parietal kinetic ataxia without proprioceptive deficit

A patient with acute onset "classic" cerebellar ataxia of the right arm without clinically detectable deep sensory loss is reported, in relation to an acute posterior parietal infarct. Wild back and forth swaying of the arm, giving away, or worsening by suppression of vision were not seen. The lesion involved area 5, parts of area 7, the angular gyrus, the middle and posterior parieto-occipital gyri, and posterior parts of the superior and middle temporal gyri. The paracentral lobule, commonly thought to be responsible for parietal ataxia, was spared. Thus posterior parietal lesions can mimick cerebellar ataxia, possibly by severing specific projections to the ventrolateral thalamic nuclei. On the basis of previous studies in primates, the superior parietal gyrus may play a major part in the ataxia presented by this patient.

Extrinsic infratentorial lesion causing ataxic hemiparesis--a new localization

The case of an 18-year-old woman is reported who had developed progressive inability to use her left limbs since the age of 13 years. Ataxic hemiparesis was noted on the left side. A CT scan of the brain revealed a non-enhancing hypodense lesion in the cerebellopontine angle with a supratentorial extension consistent with an epidermoid. Ataxic hemiparesis has previously been reported only with intrinsic lesions of the brain, except for one case. An unusual clinical localization of this entity is reported.

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

Sixteen stroke patients suffering from ataxic hemiparesis syndrome were studied with regional cerebral blood flow measured by 133-Xenon inhalation technique (12 patients) and by SPECT (HMPAO) (9 patients). The causative lesions (hematoma in 7 and infarct in 9), unilateral in 15 patients and bilateral in 1, were located in the posterior two-thirds of the corona radiata, thalamo-capsular and subthalamus regions, or cerebral peduncle. Ataxia of the cerebellar type was unilateral in 15 patients and bilateral in 1 with similar, deep, bilateral causative lesions. Four patients presented some characteristics of proprioceptive ataxia (mixed ataxia). Associated cognitive disturbances were present in 9 patients and absent in 7. Eleven of the 12 subjects studied by 133-Xenon inhalation technique showed limited centro-parietal hypoperfusion, mainly in the inferior parietal lobule, ipsilateral to the causative lesion and bilaterally in the patient with bilateral lesions and ataxia. Ipsilateral hypoperfusion was confirmed in 7/9 patients studied by SPECT, which also demonstrated contralateral cerebellar hypoperfusion in 4 patients. These findings suggest that ataxic hemiparesis syndrome results from functional depression (diaschisis) consequent to the interruption at many levels of an "inferior parietal associative cortex-cerebellar anterior lobe" circuit.

Crossed cerebellar diaschisis accompanied by hemiataxia: a PET study

To study crossed cerebellar diaschisis (CCD), cerebellar blood flow and oxygen metabolism were measured with positron emission tomography (PET) in 12 patients who showed a minimal degree of hemiparesis due to single unilateral supratentorial lesion. Six patients presenting with mild to moderate cerebellar type hemiataxia showed CCD, that is, decreased blood flow and oxygen metabolism in the cerebellar hemisphere contralateral to the side of supratentorial lesion. Hemiataxia and reduced cerebellar blood flow and metabolism occurred in the ipsilateral side. Lesions were located in the thalamus in four patients and the parietal lobe and internal capsule in one each. The other six patients did not exhibit ataxia, and oxygen metabolism was not reduced in the contralateral cerebellar hemisphere. In two of these cases, however, reduced cerebellar perfusion was observed in the contralateral cerebellar hemisphere. These findings indicate that CCD occurs with hemiataxia and suggest that it results not only from disruption of the corticopontocerebellar pathway but also of the dentatorubrothalamic pathway. CCD associated with hemiataxia, demonstrated in patients with thalamic lesions, was presumed to result from retrograde deactivation of the cerebellar hemisphere via the dentatorubrothalamic pathway.

Sensory ataxic hemiparesis in thalamic hemorrhage

Ataxic hemiparesis with cerebellar-like features has been reported following infarction or hemorrhage of the thalamus. We describe five patients with incoordination and corticospinal tract signs in the limbs opposite a dorsolateral thalamic hemorrhage. In four patients the hemorrhage extended superiorly into the lateral ventricle, the adjacent paraventricular region, and the upper and medial parts of the posterior limb of the internal capsule. Instead of cerebellar dysfunction, these patients exhibited directional errors of movement that improved distinctly when performed under visual guidance. We explain the incoordination on the basis of conscious deep sensory loss in the involved limbs. Perception of light touch, painful pinprick, and temperature were preserved in all patients. We use the term "sensory ataxic hemiparesis" to distinguish these patients from those with "classic" ataxic hemiparesis and cerebellar-like features, a distinction that may be important when planning functional rehabilitation.

Hypesthetic ataxic hemiparesis in a thalamic lacune

Right hemiparesis with an ipsilateral hypesthesia and ataxia developed in a 57-year-old man. Magnetic resonance imaging showed a left thalamic lacune bordering the medial portion of the posterior limb of the internal capsule. This finding implicated some pathogenetic mechanism of ataxic hemiparesis.