Biparietal variant of Alzheimer's disease: a rare presentation of a common disease

Abstract

Alzheimer's disease (AD) is a clinically heterogeneous disease that may have atypical presentations with focal cortical syndromes and relatively preserved episodic memory. The posterior variant of AD has two subtypes: occipitotemporal, presenting with visuoperceptive impairment, and biparietal, presenting with visuospatial dysfunction and apraxia. We report a case of a 51-year-old woman with progressive limb apraxia and choreiform movements. Her neuropsychological evaluation was compatible with dementia, and revealed ideomotor and ideational limb apraxia, severe visuoconstructive ability impairment, dyscalculia and posterior aphasia. Workup excluded metabolic, infectious, inflammatory or neoplastic causes, and hereditary conditions as Huntington's disease and familial AD. Cerebrospinal fluid biomarkers revealed β-amyloid reduction and τ protein increase. Brain imaging showed marked biparietal atrophy and hypoperfusion, and widespread cortical β-amyloid deposition. Biparietal variant of AD was diagnosed and acetylcholinesterase inhibitor treatment induced clinical stabilisation. AD may present with atypical features and a high clinical suspicion is necessary for an early diagnosis.

Figure 1

Patient copies of figures revealing constructional apraxia.

Figure 2

Brain MRI showing marked atrophy of both parietal lobes and moderate atrophy of the frontal, temporal and occipital lobes. Hippocampal volumes are relatively preserved.

Figure 3

Brain single photon emission CT scan showing severe hypoperfusion of both parietal lobes, more marked on the right, and mild hypoperfusion of frontal and temporal lobes.

Figure 4

Pittsburgh compound B (PiB) positron emission tomography showing increased β-amyloid deposition in cerebral cortex with high ¹¹C-PiB uptake in the posterior cingulated gyrus, precuneus and in the frontal, parietal, lateral temporal and occipital lobes. Increased ¹¹C-PiB uptake is also seen in caudate nuclei.