[Inverted metamorphopsia: an alteration in the perception of a special situation of objects]

This study describes the characteristics of six patients who consulted because of episodes of perceptive alteration of extrapersonal space consisting in an inversion of the situation of objects although without changes in shape or size (inverted metamorphopsia).

Six patients (4 males and 2 females) who presented episodes of inverted metamorphopsia were studied: 4 referred right-left inversion (axial plane), 1 upwards-downwards (saggital plane) and 1 inclination of environment (clockwise movement). None had any alteration in the perception of their own bodies during the episodes which lasted from 3 minutes to 1 hour, reporting from 1 to 40 episodes. The most notable antecedents were: traumatism and forced cervical posture (2), arterial hypertension (3), migraine (2), hyperlipemia (2) and protuberantial ischemia (1).

Intercritical neurologic exploration was normal. MR study showed leukoaraiosis (4), protuberantial paramedian infarctions (1) and was normal in one case of basilar migraine. Study of vestibular function (performed in 4 cases) did not show alterations. Three patients received antiepileptic drugs (1 carbamazepine and 2 gabapentin) with favorable response.

Inverted metamorphopsia is a paroxistic phenomenon which transduces a dysfunction of the posterior parietal cortex or its afferences (propioceptive, vestibular, retinian). The causes may be multiple (traumatism, migraine, ischemia). Antiepileptic drugs may have a therapeutic role in the cases with multiple episodes.