Objective: To present an unusual clinical presentation of an atypical Corticobasilar syndrome secondary to Alzheimer’s disease.

Background: Corticobasilar syndrome (CBS) typically presents with motor symptoms that are refractory to levodopa in association with apraxia, aphasia, alien-limb syndrome and diverse neuropsychiatric manifestations. CBS can be secondary to Corticobasilar Degeneration (CBS-CD), Alzheimer’s disease (CBS-AD) and Progressive Supranuclear Palsy (CBS-PSP). FDG-PET can help identify the underlying pathologic diagnosis. CBS-AD presents with a posterior temporoparietal hypometabolic pattern, including the posterior cingulate cortex (PCC) and the precuneus (PC) in the more affected hemisphere. Hypometabolism measured in the PCC or the PC is absent on other etiologies of CBS.

Method: A 58-year-old man presented to the clinic with a one-year history of worsening dysarthria and a tremor in his right hand. He exhibited resting, action, and postural tremors in his right arm, along with minimal rigidity and bradykinesia. His language abilities, including fluency, naming, repetition, and comprehension were intact. He did not show signs of speech apraxia, ideomotor limb apraxia, myoclonus, alien limb syndrome, or cortical sensory loss.

Results: Serum laboratories were normal. Brain MRI showed asymmetric brain atrophy, more pronounced in the posterior left hemisphere. Routine cerebrospinal fluid (CSF) tests were normal. Inflammatory markers and an autoimmune/paraneoplastic antibody panel were negative. The total Tau/Abeta42 ratio was 0.349, (normal ≤0.28). Symptoms did not improve with carbidopa-levodopa. An FDG-PET scan indicated abnormal hypometabolism in the parieto-temporal area and PCC. Based on his clinical presentation, CSF findings and imaging results, he was diagnosed with atypical CBS secondary to Alzheimer’s disease.

Conclusion: Alzheimer’s disease typically presents with changes in memory, language, or visual processing. However, motor-related symptoms can also occur, as in cases of CBS. This syndrome usually includes asymmetric rigidity, apraxia, cortical sensory loss, and language dysfunction. In our case, the patient exhibited only progressive dysarthria and tremors in the right hand. This clinical presentation of Alzheimer’s disease has not been previously reported and should be considered in the differential diagnosis of atypical CBS presentations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/expanding-the-spectrum-of-alzheimers-disease-clinical-presentations-progressive-dysarthria-with-monomelic-tremor/