Case report

The patient was a 67 year old, right handed, retired journalist with a history of non-systemic vasculitic polyneuropathy 3 years previously. He experienced a sudden disturbance of the visual field and became aware of his inability to recognise the faces of family members and even thought that his own reflection in the mirror was the face of a stranger. Two days later, when he came to our hospital, he was unable to recognise his doctor, but knew him by his voice. At that time, brain CT disclosed a haemorrhage in the inferolateral part of the right occipital lobe.

He was alert and oriented. He initially had a mild left homonymous hemianopia that vanished within 2 weeks (Goldmann visual field was normal). Visual acuity was 1.0 (20/20) in both eyes. Colour vision was intact with Ishihara colour plates (no achromatopsia). Ocular movements were full. The remaining cranial nerves were intact. He had remaining bilateral sensory deficit and muscle weakness in the distal parts of his four limbs due to non-systemic vasculitic polyneuropathy. No dysmetria was found. Tendon reflexes were absent and Babinski's sign was negative on both sides.

He could no longer recognise his wife or other familial people when he saw their faces. He said that he would usually identify family members and friends by non-facial, distinguishing features. He was also unable to recognise photographed faces of famous people. For example, confronted with a photograph of the Japanese sumo champion, Akebono, in front of the Meiji shrine, he could not recognise his face, but immediately named the shrine correctly.

During 3 months after the onset, the degree of his impairment in face recognition remained so severe as to interfere with daily life. Thereafter his symptoms improved to some extent, but he still reported that he was often unable to recognise the faces of famous people photographed in the newspaper. We followed him up for more than 6 months and his symptoms still remained.

BRAIN IMAGING

Brain MRI was carried out 27 days after onset. The lesion involved the right inferior occipital region at the level of the fusiform gyrus, and inferior and fourth occipital gyri, but spared the striate, lingual cortices, and parahippocampal gyrus (fig 1). N-isopropyl-(¹²³I)-p-iodoamphetamine SPECT disclosed decreased blood flow corresponding to the haemorrhage.

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Figure 1

Coronal view of the T1 weighted MR images (TM/TE= 300/ 4.2). The images show a high intensity area in the right fusiform gyrus and lateral occipital region.  

GENERAL COGNITIVE FUNCTIONING

He was alert and fully oriented to time and space, obtaining a score of 30/30 on the mini mental state examination. There was no personal change or apparent intellectual deterioration. No deficit of language or praxis was seen.3 He scored 32/36 on the Raven coloured progressive matrice (normal range). He had no memory impairment and his memory index on the Wechsler memory scale-revised (WMS-R) were normal (general memory index 96; visual memory index 104; verbal memory index 91; delayed memory index 91). Reading ability was also intact.

EXPERIMENTAL INVESTIGATIONS

Visual perception tests

He never complained of difficulty in recognising objects and places, or finding his way around places. General visual perception and visual construction were tested using the visual perception test for agnosia (VPTA),4 which is a test standardised in Japan, designed to assess higher order visual perceptual abilities. As shown in table 1, in VPTA, he performed at a normal level in all categories except for the face recognition task. He showed various deficits in the face recognition task except for perception of expression task.

In addition to VPTA, his visual performance was assessed with a battery of tests of increasing difficulty. The detail of methods and items are listed in the .

Results

As shown in table 1, he responded correctly on visual perception tests and thus, there was no evidence of any significant decline in visuoperceptual abilities. By contrast, he showed various deficits in tests of face processing. In the face matching test, his performance was slow but within the normal range. In the memory faces test, he showed a mild deficit. In the familiar faces identification test, he was able to identify only two out of 11 faces, and for most of the rest he responded that he had no idea. Of nine faces that he could not identify, he reported that only one face was encountered before. It was noted that he could neither identify nor had familiarity with his own face. In famous faces identification, he showed a severe deficit. By contrast, by identification from name, he was able to provide detailed information correctly.

Discussion

After extensive testing, our patient was found to manifest impairment restricted to the recognition of faces, due to the small lesion in the right fusiform and lateral occipital region. He demonstrated severe prosopagnosia, yet he showed no clear deficit in visual or visuospatial perception of non-facial stimuli. He showed no other abnormal findings that could possibly cause a disturbance of face recognition, such as dementia or general memory disturbance. He could also recognise common visual objects shown from both canonical and non-canonical perspectives on photographs. So far in the literature, all prosopagnosic patients who had been subjected to a detailed examination had displayed visual perceptual deficits of non-facial stimuli. Landis et al reported a prosopagnosic patient who was the first patient studied postmortem.6 They also reported that their patient was unable to identify the items when presented non-canonically. Sergent and Signoret also reported on three prosopagnosic patients who were all unable to recognise objects seen from a non-canoninal perspective.7 However, Warrington and Taylor had already pointed out that this deficit was typically associated with the right inferior parietal lesion.8 Similarly to our patient, patient OR reported by De Renzi et al 1 scored normally on tests for the objects presented from atypical views. Thus these findings provide evidence that prosopagnosia and deficits in recognising objects shown from unconventional views are distinct signs and the last is not necessarily associated with prosopagnosia.

Our patient was impaired in the task of learning unknown faces despite normal visual memory. Our data were in agreement with the contention of Takahashi et al 9 that the impairment in the ability to memorise new faces was a common feature of prosopagnosia. However, their patients were impaired on Benton's visual retention test. This dissociation in our patient's visual memory emphasised that the impairment of our patient was face specific.

Our search in the literature over the past 25 years has shown that there were only nine prosopagnosic patients so far, whose damage was confined to the right hemisphere as shown by MRI, and 10 patients by PET.1 2 9 The lesion in our patient was localised in the right fusiform, inferior, and fourth occipital gyri. Takahashiet al 9 suggested that the cortical/subcortical damage to the lingual and fusiform gyri play the most important part in prosopagnosia. However, similarly to our patient, the lingual cortex was spared in patient PC reported on by Sergent and Signoret.7 We think, therefore, that the fusiform gyrus is mainly involved in the recognition of the face.

Recent investigations of face perception in normal subjects using functional imaging techniques identified the right fusiform gyrus, and proposed that this region is primarily involved in face perception.10-14 Our present finding is consistent with these functional imaging results.