Pure alexia for kana. Characterization of alexia with lesions of the inferior occipital cortex.
OBJECTIVE
To characterize reading impairments caused by lesions in the posterior occipital cortices.


METHODS
We gave six patients with these lesions reading and writing tests and located a critical site for alexia using MRI and SPECT.


RESULTS
The patients read three-character kana (Japanese syllabograms) nonwords, and five-character kana nonwords significantly or at a near significant level more poorly and slowly than normal subjects, whereas they read kanji (Japanese morphograms) almost correctly but more slowly. Letter-by-letter reading with a single-kana character identification impairment (in five patients), a word-length effect, kinesthetic facilitation, a lexicality effect, and minor to mild agraphia for kanji (in three patients) were observed. These deficits were characteristic of pure alexia. Alexia disappeared within a few months except in one patient who had extensive hypoperfusion in the left occipital lobe. A shared lesion was located in the left posterior fusiform/inferior occipital gyri (Area 18/19) on MRI, and there was blood flow reduction around this area on SPECT. This area coincided with the activation site for kana word covert reading in our previous study.


CONCLUSIONS
These results suggest that pure alexia particularly for kana, or more generally pure alexia for letters, is caused by a lesion in the posterior inferior occipital cortex, characterized primarily by impaired kana character or letter identification, with relatively preserved kanji or word recognition.
Sakurai
Yasuhisa
Y
Department of Neurology, Mitsui Memorial Hospital, Tokyo, Japan. ysakurai-tky@umin.ac.jp
Terao
Yasuo
Y
Ichikawa
Yaeko
Y
Ohtsu
Hiroshi
H
Momose
Toshimitsu
T
Tsuji
Shoji
S
Mannen
Toru
T
D000368:Aged; D000381:Agraphia / Q000473:pathology / Q000503:physiopathology; D000704:Analysis of Variance; D001931:Brain Mapping; D004410:Dyslexia / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D007807:Language Tests; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000000981:diagnostic imaging / Q000473:pathology*; D010700:Phonetics; D011932:Reading; D021641:Recognition, Psychology / Q000502:physiology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014956:Writing