言語性幻聴を呈した橋聴覚幻覚症の1例

Verbal Hallucination in a Patient with Pontine Auditory Hallucinosis

抄録

　橋病変に伴う幻覚症状では言語性幻聴はまれである。言語性幻聴が持続し，橋梗塞が責任病変と考えられた1例を報告した。症例は66歳男性。当院初診の2年前から「左側からだけ聞える」言語性幻聴が出現し，幻聴に対する批判力は保持されていたが，幻聴が増悪したため当院を初診した。疎通性は良好であり，見当識障害や記憶障害を認めず，幻聴への批判力が保たれていたので，器質性幻覚症が疑われた。神経学的所見から橋左側の障害が示唆され，MRIでは橋底部に小虚血性病変を認めた。経過を通じてリスペリドンが幻聴に有効であった。本症例の幻聴は橋を複雑に走行する聴覚路の直接的な障害による可能性が考えられた。

　In organic hallucinosis associated with pontine lesions, episodes of verbal auditory hallucination have been rarely reported. A 66-year-old male with verbal auditory hallucination induced by pontine lacunar infarction was presented. Heavy drinking had been noted since three years before the onset of the symptoms. Threatening verbal auditory hallucination had continued since two years before his initial visit to our hospital. His auditory hallucination was experienced only on the left side. Although he developed transient delusional reaction, he soon acquired and continued to use critical thinking concerning his own hallucinatory symptom. No other psychotic symptoms had ever been experienced. In our initial interview, he revealed partial reality testing to his own curious experiences and could also understand our medical explanation for the pathogenesis of his symptoms. We considered that the cause of some neurological signs including left nystagmus, ptosis, facial nerve palsy, and hearing loss could be attributable to the disturbance in the left lower pons or midbrain. The MRI showed small ischemic lesions in the lower pons. Schizophrenia, alcoholic hallucinosis or other clinical disorders could be differentiated on the basis of these clinical manifestations and MRI findings. Risperidone was effective for controlling this verbal halluciantion. The characteristic auditory hallucination in this patient was able to be explained by the direct injury of the auditory nervous system in the pons.