Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 3, 2011, pp. 482-484

Neurology India, Vol. 59, No. 3, May-June, 2011, pp. 482-484

Letter to Editor

Posterior cortical atrophy: A rare visual variant of Alzheimer's disease

Amit Arora, Chandra M Sharma, BL Kumawat, Dinesh Khandelwal

Department of Neurology, SMS Medical College and Hospital, Jaipur, India

Correspondence Address: Amit Arora Department of Neurology, SMS Medical College and Hospital, Jaipur India doc_amitarora@yahoo.com

Date of Submission: 03-May-2011
Date of Decision: 04-May-2011
Date of Acceptance: 04-May-2011

Code Number: ni11144

PMID: 21743197

DOI: 10.4103/0028-3886.82760

Sir,

We read the article by Gafoor et al. ^[1] on posterior cortical atrophy with great interest. We wish to report a case with similar radiological features but with a different clinical presentation.

A 55-year-male, right-handed and high-school educated, was admitted for insidious-onset reading and writing difficulty of 5 years duration. He had earlier been evaluated by several ophthalmologists. He used to read letter by letter rather than whole words and had difficulty focussing at a single line while reading. He had noticed change in size, shape and configuration of individual letters while writing, forcing him to change his bank security signature to a thumb impression. He had difficulty in reaching out to touch or pick up an object, mislocating them even though he claimed that he could clearly see the object. He also had difficulty in recognizing faces and could do so only after hearing the person's voice. There was no history of forgetfulness, difficulty in remembering path or in wearing clothes, hallucinations or behavioral disturbances. His past and family history was not significant. He had insidious-onset difficulty in walking especially downhill with asymmetric stiffness of all four limbs since 2 years.

Clinical examination revealed a conscious, alert patient with normal vital parameters. Mini-Mental Status Examination (MMSE) score was 28/30 with constructional apraxia. Higher mental function evaluation revealed affection of parietal and occipital lobes with optic ataxia, visual inattention, alexia, dysgraphia and prosopagnosia. Color vision was normal. Frontal and temporal lobe functions including memory and behavior were normal and so also judgement and insight. Visual acuity and Fundus examination was normal. Visual field evaluation by confrontation method showed inferior altitudinal field defect. There were mild asymmetric (predominantly right-sided) extrapyramidal signs with mainly cogwheel rigidity and brisk Deep Tendon Reflexes (DTR). There was no evidence of limb apraxia, cortical sensory loss, or alien limb phenomenon.

Hematological and biochemical parameters including thyroid profile, serum vitamin B ₁₂ levels, and HIV status were normal. Magnetic resonance imaging (MRI) of brain showed selective cortical atrophy involving the parietal and occipital lobes bilaterally [Figure - 1] and [Figure - 2].

As compared to the patient described by Gafoor et al., our patient had prominent dysgraphia and alexia, along with acalculia, and ocular apraxia, suggesting predominant parietal lobe involvement manifesting as both ventral and dorsal stream affection; thus, this patient had few features of both Balint syndrome and Gerstmann syndrome. This is in contrast to the initial description of posterior cortical atrophy by Benson et al., where they said that the condition presented with the complete features of both these syndromes. ^[2] Our patient met all the important diagnostic criteria of posterior cortical atrophy, and besides, MRI showed predominant focal atrophy of the parieto-occipital lobes. Our patient had asymmetric extrapyramidal signs raising a possibility of Corticobasal Ganglionic Degeneration (CBGD) being the etiology; however, despite the illness having been present for such a long duration, eminent features of CBGD such as cortical sensory loss, alien limb phenomenon, memory disturbances, and myoclonus were absent .Tang wei et al. and various other authors have described both CBGD and Alzheimer disease in etiological pathogenesis of posterior cortical atrophy. ^[3] Hence, instead of the older term 'visual variant of Alzheimer disease,' the more descriptive and broader term 'progressive posterior cortical dysfunction has been suggested to encompass other diseases manifesting as a syndrome with predominant focal affection of posterior parietal and occipital lobes and comparative sparing of temporal and frontal lobes. ^[4] Whether the primary etiology of posterior cortical atrophy is Alzheimer disease or whether it is a manifestation of a spectrum of other disorders with primarily posterior lobes affection, can be confirmed only by neuropathological evaluation.

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