Posterior cortical atrophy presenting with agraphia for kanji and statokinetic dissociation (Riddoch phenomenon): a case report

We report a patient with posterior cortical atrophy (PCA) who manifested as agraphia for kanji and statokinetic dissociation (Riddoch phenomenon). A 52-year-old, right-handed woman complained that beginning at age 50, she could write only kana (a phonographic script) but not kanji (a morphographic script). She could not write even her own name in kanji. Neuropsychologic examinations disclosed kanji-dominant agraphia, acalculia, right-left disorientation, finger agnosia, constructional apraxia, and simultanagnosia. Many of these, including agraphia, are components of Gerstmann syndrome. She manifested no aphasia or alexia, while not only writing but also copying of kanji was impaired. Speech functions, behavior, and personality were relatively spared. The patient also displayed statokinetic dissociation (Riddoch phenomenon): kinetic Goldmann fields were normal, but static Humphrey visual fields showed an incongruous right homonymous hemianopsia. MRI showed atrophy of the left parietal lobe. ^99mTc ethyl cysteinate dimer (ECD) single-photon emission computed tomography (SPECT) showed hypoperfusion , predominantly in the left hemisphere and especially left the parietal lobe . These clinical and neuroradiologic findings are consistent with PCA. In patients with PCA, suspected incomplete homonymous hemianopsia should be confirmed with a Humphrey visual field test. Ishihara pseudoisochromatic plates may not be reliable; color vision should be checked using the panel D-15 test.