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    • br Discussion The patient presented initially only with pari

    2023-12-12


    Discussion The patient presented initially only with parietal symptoms in the form of acalculia, visuo-spatial deficits, and visuo-perceptual deficits and dressing apraxia. He also had simultognosia as early symptoms. Later when the disease progressed he had recent memory deficits and language involvement. Based on the pattern of cognitive deficits described above and the presence of severe hypometabolism of bilateral parietal lobe finding on PET-CT brain, a diagnosis of Posterior cortical atrophy was made as per the consensus classification by Crutch et al. (2017). The typical age of onset of PCA is between 50 and 65 years which is younger compared to the common presentation of AD (McMonagle et al., 2006; Mendez et al., 2002). There are no population based prevalence studies of PCA. This might be due to lack of consistent criteria for PCA and also due to the rarity of this condition in elderly population. A study by Snowden et al. reported a prevalence of 5% among 523 consecutive AD patients presenting to their facility (Snowden et al., 2007). There is conflicting evidence for specific gender preference in PCA (Mendez et al., 2002; Renner et al., 2004). PCA has distinct clinical features compared to AD and other dementia syndromes. In case series of 15 PCA patients described by Charles et al., 60% had visual symptoms and 46% had alexia. Nearly 53% of PCA patients also had memory decline (Charles and Hillis, 2005). In another study by Tang Wai et al. of 40 PCA patients, nearly 87.5% patients have one or more features of Balint’s syndrome. Balint’s syndrome features are simultognosia, ocular apraxia and optic ataxia. All the three symptoms of Balint’s syndrome were present in only three patients. In the same study 61% of patients had one or more feature of Gerstmann syndrome that includes agraphia, acalculia, left to right confusion and finger anomia (Tang-Wai et al., 2004). In PCA compared to typical AD the structural imaging there is predominant atrophy of parietal lobes and occipital lobes compared to medial temporal lobes. Studies reported (-)-MK 801 australia atrophy of parietal lobes with right being more atrophied than left (Lehmann et al., 2011; Whitwell et al., 2007). Functional imaging (SPECT and PET) studies also reported similar areas of involvement as with structural imaging showing decreased metabolism of parietal and occipital lobes. In addition FDG-PET studies reported decreased metabolism in frontal eye fields and this is secondary to reduction in input from occipital lobes (Gardini et al., 2011; Kas et al., 2011; Nestor et al., 2003).In our case there is significant reduction in metabolism of bilateral parietal lobes. PCA is a syndrome presenting with cluster of specific cognitive and unique radiological finding. The underlying pathogenesis for PCA differs from case to case. Majority of neuropathological studies done so far reported that Alzheimer’s disease is most common etiology. The other less common etiological causes are lewybody disease (LBD), Corticobasal degeneration (CBD) and Prion disease (Renner et al., 2004; Tang-Wai et al., 2004). In clinical sample the etiology of Alzheimer’s disease can be confirmed by CSF amyloid Aβ42 and tau ratio or amyloid PET imaging (Crutch et al., 2017). LBD and CBD presents with extrapyramidal symptoms along with PCA features. In these cases the etiological diagnosis is possible by excluding the Amyloid pathogenesis. In our cases even though we didn’t do the CSF amyloid Aβ42 and tau ratio or amyloid PET imaging, involvement of recent episodic memory in later stage and absence of extrapyramidal features made us to make a diagnosis of PCA phenotype with probable AD etiology. There are no specific treatments for PCA. As PCA patients have specific visuo-spatial and visuo-perceptual deficits with minimal memory deficits in earlier stages, these patients undergone extensive evaluation and sometimes goes to other specialities such as ophthalmologist before reaching definitive diagnosis. In AD and LBD presenting as PCA phenotype, acetylcholinesterase inhibitors are found to be useful (Kim et al., 2005). Many patients with PCA have preserved insight and intact memory and language atleast in early stage, and due to these factors patients with PCA are suitable for cognitive retraining. There are reports on cognitive training and its usefulness in PCA patients(Roca et al., 2010; Weill-Chounlamountry et al., 2016).