Recurrent transient topographical amnesia: a patient with frequent episodes

Topographical disorientation is a condition in which a subject becomes disoriented in familiar surroundings [1]. The selective deficit of topographical disorientation is relatively rare and has been attributed to cerebrovascular disease, Alzheimer’s disease, and frontotemporal dementia [1–3]. Recently, cases of transient topographical amnesia (TTA) have been published [4–7]. These cases are characterized by a sudden onset and short-lasting disturbance in orientation without any loss of consciousness or episodic memory. The patients soon recover completely, and their prognosis seems good without progression to dementia or physical disability. We report a patient who had recurrent episodes of TTA, which gradually worsened over 16 years. The patient was a 61-year-old right-handed man, with 9 years of formal education. His birth and development were normal, and there was no history of neurological disease in his family. His first episode of topographical disorientation occurred at 45 years of age, when he was driving his car along familiar roads. The episode lasted for only several seconds, and immediately following he was reorientated. These episodes first occurred once a year, but gradually increased in frequency with time. The attacks also occurred while walking and occasionally their duration was close to 1 min. At age 61, he experienced these episodes a few times a month, and then visited our hospital. He described the episodes as follows: ‘‘I was driving my car to go home from the office. I suddenly became insensible even to familiar sights. I could not recognize the buildings and bridges for pedestrians while I should know them. Then, they became clear several seconds later.’’ During the episode, he was alert and well-oriented. He was aware of, and memorized his attack, and could describe it later in detail. Neuropsychological evaluation of memory and abstract logical abilities proved normal by means of standardized tests (Table 1). There were no abnormalities in his neurological examination, or in his complete blood count, serum biochemistry including thyroid function and vitamins, Holter electrocardiogram, repeated electroencephalogram (EEG), brain magnetic resonance imaging (MRI) and angiography, with the exception of [I]iodoamphetamine single photon emission computed tomography (SPECT) performed 2 weeks after the last attack, showing hypoperfusion in the inferolateral surface of bilateral occipital lobes (Fig. 1). Repeated EEGs revealed no abnormalities and carbamazepine medication failed to improve his symptoms, although epilepsy was suspected as the pathogenic mechanism. Transient topographical amnesia is a rare symptom, and previous literature reported that some episodes are caused by transient ischemic attack [8], migraine [9], normal pressure hydrocephalus [10], and epilepsy [7, 11]. The etiology of TTA remains unknown. Most patients with TTA are healthy middle-aged or elderly people, and A. Shindo (&) H. Tomimoto Department of Neurology, Mie Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan e-mail: a-shindo@clin.medic.mie-u.ac.jp