Introduction

Topographic disorientation (TD) denotes selective loss of a patient’s ability to find their way within their environment, and is grossly divided into two types: landmark (scene) agnosia and defective route finding.

Aguirre and D’Esposito categorized TD into four types based on neuroanatomical and neuropsychological similarities, and reported that, to find one’s way about, it is necessary to be able to recognize familiar buildings, signals, and other landmarks in the surrounding (defective in landmark agnosia TD), to represent one’s (egocentric) position with respect to any present landmark (defective in egocentric disorientation), to use more abstract representations to create an idea of the particular direction to follow to reach a particular destination (defective in heading disorientation), and to learn and update information depending on new or changed environments (defective in anterograde disorientation) [1]. Additionally, two types of route finding have been proposed. Egocentric spatial representation involves the processing of an object’s localization with reference to the patient’s body or position, while allocentric spatial representation involves the spatial relationship between objects in the environment. Few reports have described cases of TD with allocentric and/or egocentric spatial impairment. Here, we report a patient with TD due to infarction, where the lesion included the right parahippocampal gyrus (PHG), involved in both types of spatial recognizing functions [2, 3], who showed both allocentric and egocentric spatial impairment.

Case report

A 57-year-old, right-handed man presented to a hospital with severe headache and left-sided visual loss. Brain magnetic resonance imaging (MRI) revealed an old infarct involving the right inferior temporal and occipital lobes. The patient’s family noted that he had difficulty in finding routes to destinations. Over the course of 6 months, he repeatedly became lost en route to a familiar workplace and misidentified the customer’s entrance for the workers’ entrance. After being admitted to our hospital by his family, he became lost in the hospital corridor whenever he left his room, and could not find his way without assistance. After some weeks, he gradually learned his way around the hospital corridors and garden, using store signs as landmarks.

Clinical observations

Neurological examination revealed left hemianopsia. Tendon reflexes, all sensory modalities, coordination, gait, and posture were normal. No abnormalities were found upon blood and cerebrospinal fluid examination. No epileptic discharge was observed in two separate electroencephalograms. Brain MRI revealed that the old infarct lesion included the PHG (Fig. 1).

Fig. 1
figure 1

Magnetic resonance imaging of the brain. An axial T2-weighted image of the present patient shows an old ischemic lesion, including the posterior part of parahippocampal gyrus (PHG), fusiform gyrus, and lingual gyrus—structures supplied by the right posterior cerebral artery

Full size image

Global cognitive function (The Mini Mental State Examination 28/30) was preserved, as was intelligence (The Wechsler Adult Intelligence Scale-Revised IQ102); however, there was a discrepancy between verbal (112) and performance IQ (88). The Wechsler Memory Scale-Revised results were 98 for the Verbal Memory Index, 83 for the Visual Memory Index, 92 for the General Memory Index, 106 for Attention, 110 for Attention Index, and below 50 for the Delayed Memory Index. The Stroop and clock drawing tests were normal.

Limb kinetic, ideomotor, and buccofacial apraxia were absent. A naming task of 24 famous persons and a matching task of 12 unknown persons’ photographs were all correct. He had no prosopagnosia. The Boston Naming Test in Japanese was 100% correct (60/60). There was no unilateral neglect, based on the result of drawing a picture of a flower and a crossing-out task. A total of 107 of 110 line figures were named correctly. Although all 36 complex figures in the Rey–Osterrieth complex-figure test were correctly copied, the recall task 3 min later was less than −2 SD, with 6 points recalled very poorly. On the Benton Visual Retention test, the number of items answered correctly was 5–7 score, while the number answered incorrectly were 4–6 score, indicating a slight impairment.

Taken together, he had normal attention, orientation, intelligence, executive function, verbal learning, and memory, had no hemispacial neglect, prosopagnosia, aphasia, or apraxia, and scored within the normal range for visuoperceptual, visuospatial, and visuoconstructive abilities. However, he showed impairments in visual and visuospatial learning, and recall.

Clinical tests for topographical disorientation

The patient could correctly locate and identify various Japanese cities on a map. He could recognize 24 famous worldwide monuments. We asked his wife to take digital pictures of potential landmarks on his route for commuting from his house to the nearby station. He was then asked to choose the appropriate direction to take to the station (turn right, left, or go straight at each turning point and crossing) based on the digital pictures (similar to test 2 presented by Wilson [4]). The rate of correct answering was no different from that obtained by chance. He could name and recognize 20 of 23 houses, public buildings, and landmarks in his neighborhood from the digital photographs, but appeared confused when asked to describe their location in terms of distance and direction from his house. It seemed that he failed to match the familiar landscape in the photographs with his imaging representations. He mislocated the entrance to a tunnel far from his home as being near his house and a driveway near his house as a private road on his property. Thus, his difficulties were confined to recall or recollection of local landmarks in an appropriate spatial context in each scene.

He could draw the room placement in his house fairly precisely (Fig. 2), but failed to sketch a novel place, such as the hospital. He recognized the actual room arrangement in the hospital in a mirror image. However, he incorrectly recognized the relative locations of different landmarks or rooms that were nearer or further from each other, or to the right or left (Fig. 3).

Fig. 2
figure 2

Drawing of the patient’s house. a The illustration of the room placement in his house made by his wife. b We asked the patient to draw an illustration of room placement of his house from memory. He could draw room placements fairly correctly. However, the position and direction of stairs was incorrect, the location of the living room and Japanese style room were swopped

Full size image
Fig. 3
figure 3

Drawing of the hospital room. a The actual illustration of the room arrangement in the hospital. b The map drawn by the patient showed dislocation, i.e., a mirror image

Full size image

Discussion

We here describe a patient with TD who had difficulty finding his way to familiar places and novel environments, even though he could identify the relevant landmarks; therefore, he did not have landmark agnosia. Based on failing test 2 in Wilson’s report [4], we consider that he suffered from egocentric disorientation. However, his failure in retrieving local landmarks from his own residential area may reflect impaired processing of allocentric spatial representations. His ability to draw a map of familiar and unfamiliar places indicated partial damage of his visuospatial learning and memory. These mistakes, such as mirroring of spatial locations and turning in the wrong direction at a corner, are suspicious of impaired egocentric coordinates. We speculate that his TD, which arose from egocentric or allocentric spatial impairment, was difficult to correct due to the disturbed, albeit mildly so, visual and visuospatial memory. Within the taxonomy of Aguirre and D’Esposito [1], his failure to find a route is characteristic of both egocentric disorientation and anterograde disorientation with allocentric disorientation. Considering the house or the hospital room as an extension of the patient’s body, his TD can be interpreted as egocentric disorientation.

Other patients with a similar brain lesion associated with TD have been reported [2, 5]. Temporal lobe epilepsy patients with right posterior PHG lesions have shown impairment in an egocentric virtual maze acquisition task [5], while a patient with TD after infarction of the right mediotemporooccipital lobe, including the PHG, has demonstrated both allocentric and egocentric spatial impairment [2]. Animal studies have verified the role of the hippocampus (HIP) in allocentric spatial memory, although recent studies have suggested that the HIP is also concerned with egocentric spatial memory [5–8]. In rats, HIP cells associated egocentric motor information with allocentric spatial information [9], and associated visual cues with body turning [6]; in chicks, memory formation was associated with egocentric spatial relationships [7], while, in monkeys, the HIP represented information about whole-body motion [10]. In a mouse model with a hippocampal lesion, mice presented with a star maze revealed allocentric as well egocentric memory effects [8].

In conclusion, we here reported a patient with TD arising from a right PHG lesion that produce both allocentric and egocentric spatial disturbances, as well as impairments of visuospatial learning and memory. The definition of “allocentric” or “egocentric” is somewhat arbitrary, and the interpretation of these two different TD situations should be clarified to develop a universal diagnostic battery for differentiating TD types.