Objective: To describe a case of a 54-year-old woman diagnosed with atypical corticobasal syndrome (CBS). Neuropathological studies revealed that she had thalamic dementia with motor neuron disease (MND). 

Background: Thalamic dementia with MND is a rare pathologic entity that has been previously described once in a patient with cognitive decline, aphasia, progressive rigidity, and quadriparesis (1). Earlier studies reported thalamic involvement in cases of familial MND, but were not associated with dementia (2). This pathology has not been previously associated with CBS.

Methods: We report the clinical evaluation, diagnostic studies and neuropathological findings of a person with thalamic dementia and MND. 

Results: Our patient, a 54 year-old right-handed woman, developed right leg weakness, followed by behavioral disturbances, dysarthria, cognitive decline, and gait difficulty. There was a maternal family history of cognitive decline and gait disorder. Her exam was notable for asymmetric bradykinesia, rigidity, and gait apraxia, which were not responsive to levodopa. She was diagnosed with atypical CBS. She clinically deteriorated over the course of eight years, and developed asymmetric spastic quadriparesis, myoclonus, and seizures, which localized to the frontal lobe. Brain MRI revealed diffuse atrophy. Cervical spine MRI was normal. There was mildly decreased glucose metabolism in the region of the frontal lobes on FDG-PET. CSF studies revealed elevated protein. EMG was normal. Transcranial magnetic stimulation demonstrated left more than right central pathology. Sequential neuropsychological testing revealed deficits in memory, executive, and visuospatial function. Neuropathologic examination demonstrated paracentral, frontal, and parietal atrophy, and neuronal loss and gliosis within the dorsomedian nucleus of the thalamus, sparing the sensory and motor nuclei. Demyelination of the lateral corticospinal tract was noted, indicative of MND. No pathologic inclusions were detected.

Conclusions: Thalamic dementia with MND is a rare neuropathological diagnosis, which may be considered in cases of atypical CBS. Parkinsonism was a minor feature of her presentation and spasticity and behavioral changes were significant features, emphasizing that our case is not typical of CBS.

References: 1.) Deymeer F, Smith TW,  DeGirolami U, Drachman DA. Thalamic dementia and motor neuron disease. Neurology. 1989;39:58-61.

2.) Brownell B, Oppenheimer DR, Hughes JT. The central nervous system in motor neuron disease. J Neurol Neurosurg Psychiatry 1970;33:338-375. 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/gait-impairment-and-cognitive-changes-in-a-case-of-thalamic-dementia-and-motor-neuron-disease/