Prosopagnosia following nonconvulsive status epilepticus associated with a left fusiform gyrus malformation

Prosopagnosia: face blindness and its association with neurological disorders

Loss of facial recognition or prosopagnosia has been well-recognized for over a century. It has been categorized as developmental or acquired depending on whether the onset is in early childhood or beyond, and acquired cases can have degenerative or non-degenerative aetiologies. Prosopagnosia has been linked to involvement of the fusiform gyri, mainly in the right hemisphere. The literature on prosopagnosia comprises case reports and small case series. We aim to assess demographic, clinical and imaging characteristics and neurological and neuropathological disorders associated with a diagnosis of prosopagnosia in a large cohort. Patients were categorized as developmental versus acquired; those with acquired prosopagnosia were further subdivided into degenerative versus non-degenerative, based on neurological aetiology. We assessed regional involvement on [18F] fluorodeoxyglucose-PET and MRI of the right and left frontal, temporal, parietal and occipital lobes. The Intake and Referral Center at the Mayo Clinic identified 487 patients with possible prosopagnosia, of which 336 met study criteria for probable or definite prosopagnosia. Ten patients, 80.0% male, had developmental prosopagnosia including one with Niemann-Pick type C and another with a forkhead box G1 gene mutation. Of the 326 with acquired prosopagnosia, 235 (72.1%) were categorized as degenerative, 91 (27.9%) as non-degenerative. The most common degenerative diagnoses were posterior cortical atrophy, primary prosopagnosia syndrome, Alzheimer's disease dementia and semantic dementia, with each diagnosis accounting for >10% of this group. The most common non-degenerative diagnoses were infarcts (ischaemic and haemorrhagic), epilepsy-related and primary brain tumours, each accounting for >10%. We identified a group of patients with non-degenerative transient prosopagnosia in which facial recognition loss improved or resolved over time. These patients had migraine-related prosopagnosia, posterior reversible encephalopathy syndrome, delirium, hypoxic encephalopathy and ischaemic infarcts. On [18F] fluorodeoxyglucose-PET, the temporal lobes proved to be the most frequently affected regions in 117 patients with degenerative prosopagnosia, while in 82 patients with non-degenerative prosopagnosia, MRI revealed the right temporal and right occipital lobes as most affected by a focal lesion. The most common pathological findings in those with degenerative prosopagnosia were frontotemporal lobar degeneration with hippocampal sclerosis and mixed Alzheimer's and Lewy body disease pathology. In this large case series of patients diagnosed with prosopagnosia, we observed that facial recognition loss occurs across a wide range of acquired degenerative and non-degenerative neurological disorders, most commonly in males with developmental prosopagnosia. The right temporal and occipital lobes, and connecting fusiform gyrus, are key areas. Multiple different pathologies cause degenerative prosopagnosia.

Surgical Management of Temporal Lobe Epilepsy Secondary to Epidermoid Cysts: A Case Report With Review of the Literature

Epidermoid cysts represent roughly 1% of all intracranial tumors. They are frequently located in the cerebellopontine angle but rarely extend to the supratentorial brain. Epilepsy is an extremely uncommon manifestation of this neoplasm. We suggest the surgical management of a 35-year-old male who presented with a six-month history of intractable temporal lobe epilepsy. His seizures were characterized by a focal onset in the form of déjà vu experiences, followed by a secondarily generalized tonic-clonic seizure. Imaging revealed a heterogeneous cystic mass in the right cerebellopontine angle, extending supratentorially causing a mass effect on the mesial temporal region. Gross total resection was achieved through a combined subtemporal-retrosigmoid approach. Histopathology revealed an epidermoid cyst. The patient was entirely seizure-free at the three-month follow-up. Epidermoid cysts may present with epileptic seizures. Seizure freedom can be achieved with surgical management in most cases. The patient's symptoms, imaging findings, and epileptogenic focus must be considered to select the appropriate surgical strategy.

Face processing in the temporal lobe

Face perception is a socially important but complex process with many stages and many facets. There is substantial evidence from many sources that it involves a large extent of the temporal lobe, from the ventral occipitotemporal cortex and superior temporal sulci to anterior temporal regions. While early human neuroimaging work suggested a core face network consisting of the occipital face area, fusiform face area, and posterior superior temporal sulcus, studies in both humans and monkeys show a system of face patches stretching from posterior to anterior in both the superior temporal sulcus and inferotemporal cortex. Sophisticated techniques such as fMRI adaptation have shown that these face-activated regions show responses that have many of the attributes of human face processing. Lesions of some of these regions in humans lead to variants of prosopagnosia, the inability to recognize the identity of a face. Lesion, imaging, and electrophysiologic data all suggest that there is a segregation between identity and expression processing, though some suggest this may be better characterized as a distinction between static and dynamic facial information.

Is human face recognition lateralized to the right hemisphere due to neural competition with left-lateralized visual word recognition? A critical review

The right hemispheric lateralization of face recognition, which is well documented and appears to be specific to the human species, remains a scientific mystery. According to a long-standing view, the evolution of language, which is typically substantiated in the left hemisphere, competes with the cortical space in that hemisphere available for visuospatial processes, including face recognition. Over the last decade, a specific hypothesis derived from this view according to which neural competition in the left ventral occipito-temporal cortex with selective representations of letter strings causes right hemispheric lateralization of face recognition, has generated considerable interest and research in the scientific community. Here, a systematic review of studies performed in various populations (infants, children, literate and illiterate adults, left-handed adults) and methodologies (behavior, lesion studies, (intra)electroencephalography, neuroimaging) offers little if any support for this reading lateralized neural competition hypothesis. Specifically, right-lateralized face-selective neural activity already emerges at a few months of age, well before reading acquisition. Moreover, consistent evidence of face recognition performance and its right hemispheric lateralization being modulated by literacy level during development or at adulthood is lacking. Given the absence of solid alternative hypotheses and the key role of neural competition in the sensory-motor cortices for selectivity of representations, learning, and plasticity, a revised language-related neural competition hypothesis for the right hemispheric lateralization of face recognition should be further explored in future research, albeit with substantial conceptual clarification and advances in methodological rigor.

Prosopagnosia and disorders of face processing

Face recognition is a form of expert visual processing. Acquired prosopagnosia is the loss of familiarity for facial identity and has several functional variants, namely apperceptive, amnestic, and associative forms. Acquired forms are usually caused by either occipitotemporal or anterior temporal lesions, right or bilateral in most cases. In addition, there is a developmental form, whose functional and structural origins are still being elucidated. Despite their difficulties with recognizing faces, some of these subjects still show signs of covert recognition, which may have a number of explanations. Other aspects of face perception can be spared in prosopagnosic subjects. Patients with other types of face processing difficulties have been described, including impaired expression processing, impaired lip-reading, false familiarity for faces, and a people-specific amnesia. Recent rehabilitative studies have shown some modest ability to improve face perception in prosopagnosic subjects through perceptual training protocols.

Prosopagnosia seizure semiology in a 10-year-old boy: a functional neuroimaging study

We illustrate a case of post-traumatic recurrent transient prosopagnosia in a paediatric patient with a right posterior inferior temporal gyrus haemorrhage seen on imaging and interictal electroencephalogram abnormalities in the right posterior quadrant. Face recognition area mapping with magnetoencephalography (MEG) and functional MRI (fMRI) was performed to clarify the relationship between the lesion and his prosopagnosia, which showed activation of the right fusiform gyrus that colocalised with the lesion. Lesions adjacent to the right fusiform gyrus can result in seizures presenting as transient prosopagnosia. MEG and fMRI can help to attribute this unique semiology to the lesion.

Selective defects of face familiarity associated to a left temporo-occipital lesion

Acquired prosopagnosia is usually a consequence of bilateral or right hemisphere lesions and is often associated with topographical disorientation and dyschromatopsia. Left temporo-occipital lesions sometimes result in a face recognition disorder but in a context of visual object agnosia with spared familiarity feelings for faces, usually in left-handers. We describe a patient with a left temporo-occipital hemorrhagic lesion unexpectedly resulting in a deficit of face familiarity, which could represent a mild form of associative prosopagnosia. Our patient failed to feel familiarity feelings even with very well-known famous faces but had neither visual object agnosia nor defects with semantics or naming of celebrities. This was confirmed even when the patient was re-tested a year later. We speculate that a graded lateralization of face processing could be at the basis of occasional cases of prosopagnosia.

Examining the effects of inversion on lateralisation for processing facial emotion

There is an increasing amount of evidence which suggests that each hemisphere is differently specialised for processing facial stimuli, with the right hemisphere specialised for the processing of configural information and the left hemisphere specialised for the processing of featural information. While there is evidence for this distinction from studies of face recognition, it has not been shown in studies of lateralisation for processing facial emotion. In this study the chimeric faces test was used with faces expressing anger, disgust, fear, happiness, sadness or surprise, presented in either an upright or an inverted orientation. When presented upright, a significant right hemisphere bias was found for all six emotions. However, when inverted, a significant left hemisphere bias was found for the processing of happiness and surprise, but not for the processing of negative emotions (although the analysis was approaching significance for anger). These findings support the hypothesis that each hemisphere is differently specialised for processing facial emotion, but contradicts previous work that examined the effects of inversion on chimeric face stimuli.

Who is who: areas of the brain associated with recognizing and naming famous faces

OBJECT

It has been hypothesized that specific brain regions involved in face naming may exist in the brain. To spare these areas and to gain a better understanding of their organization, the authors studied patients who underwent surgery by using direct electrical stimulation mapping for brain tumors, and they compared an object-naming task to a famous face-naming task.

METHODS

Fifty-six patients with brain tumors (39 and 17 in the left and right hemispheres, respectively) and with no significant preoperative overall language deficit were prospectively studied over a 2-year period. Four patients who had a partially selective famous face anomia and 2 with prosopagnosia were not included in the final analysis.

RESULTS

Face-naming interferences were exclusively localized in small cortical areas (< 1 cm2). Among 35 patients whose dominant left hemisphere was studied, 26 face-naming specific areas (that is, sites of interference in face naming only and not in object naming) were found. These face naming-specific sites were significantly detected in 2 regions: in the left frontal areas of the superior, middle, and inferior frontal gyri (p < 0.001) and in the anterior part of the superior and middle temporal gyri (p < 0.01). Variable patterns of interference were observed (speech arrest, anomia, phonemic, or semantic paraphasia) probably related to the different stages in famous face processing. Only 4 famous face-naming interferences were found in the right hemisphere.

CONCLUSIONS

Relative anatomical segregation of naming categories within language areas was detected. This study showed that famous face naming was preferentially processed in the left frontal and anterior temporal gyri. The authors think it is necessary to adapt naming tasks in neurosurgical patients to the brain region studied.

Prosopagnosia associated with a left occipitotemporal lesion

Acquired prosopagnosia is usually associated with bilateral or right-sided lesions of the occipital or temporal lobes. In rare cases of prosopagnosia after left-sided lesions in left-handed subjects, it is attributed to a reversed hemispheric specialization for face processing. This study examines the face-processing functions of a left-handed prosopagnosic patient with a left-sided lesion affecting the region of the occipital face area and possibly the fusiform face area, to contrast his deficits with those of prosopagnosic patients with right-hemispheric lesions. Similar to those patients, he has a moderately severe reduction in familiarity judgments, is impaired in processing face configuration, and shares with some of those patients a greater failure to process eye than mouth information, indicating an altered pattern of facial saliency. He has a mild reduction in the identification of exemplars of non-face objects. Unlike those patients, he has better residual familiarity on a two-alternative forced-choice task and can processing facial configuration if given more time, indicating a reduction in efficiency rather than a severe limitation. He has more difficulty accessing semantic-biographic information from names. He has trouble with facial feature imagery but not imagery for global face shape. Thus this subject's deficits represent a combination of impaired familiarity and configuration processing (normally right-sided functions in right-handed subjects), and impaired feature processing and access to semantic-biographic information (normally left-sided functions). His prosopagnosia likely reflects partially anomalous rather than reversed lateralization of hemispheric perceptual functions.