Anti–NMDA Receptor Encephalitis Associated With Transient Cerebral Dyschromatopsia, Prosopagnosia, and Lack of Stereopsis

Visual Pathway Involvement in NMDA Receptor Encephalitis: A Clinical, Optical Coherence Tomography, and 18-Fluorodeoxyglucose PET/CT Approach

BACKGROUND

Anti-NMDA receptor (NMDAR) encephalitis patients have been reported to exhibit visual dysfunction without retinal thinning. The objective of our study was to examine the involvement of the visual pathway structure and function in anti-NMDAR encephalitis by assessing postrecovery visual function and retinal structure, and acute-phase occipital cortex function.

METHODS

In this cross-sectional study, patients diagnosed with anti-NMDAR encephalitis per consensus criteria underwent postrecovery visual acuity (VA) testing and optical coherence tomography (OCT) with automated retinal layer segmentation. Clinical data and acute-phase brain 18F-fluorodeoxyglucose (FDG) PET/CT (performed within 90 days of symptom onset, assessed qualitatively and semi-quantitatively) were retrospectively analyzed. VA and OCT measures were compared between anti-NMDAR and age, sex, and race-matched healthy controls (HC). When available, FDG-PET/CT metabolism patterns were analyzed for correlations with VA, and OCT measures.

RESULTS

A total of 16 anti-NMDAR (32 eyes) and 32 HC (64 eyes) were included in the study. Anti-NMDAR exhibited lower low-contrast VA (2.5% contrast: -4.4 letters [95% CI; -8.5 to -0.3]; P = 0.04, 1.25% contrast: -6.8 letters [95%CI; -12 to -1.7]; P = 0.01) compared with HC, but no differences were found on OCT-derived retinal layer thicknesses. Acute-phase FDG-PET/CT medial occipital cortex metabolism did not correlate with follow-up low-contrast VA or ganglion cell/inner plexiform layer thickness (GCIPL) (n = 7, 2.5% contrast: r = -0.31; P = 0.50, 1.25% contrast: r = -0.34; P = 0.45, GCIPL: r = -0.04; P = 0.94).

CONCLUSIONS

Although the visual system seems to be involved in anti-NMDAR encephalitis, no retinal structural or occipital cortex functional abnormalities seem to be responsible for the visual dysfunction. When detected acutely, occipital lobe hypometabolism in anti-NMDAR encephalitis does not seem to associate with subsequent retrograde trans-synaptic degenerative phenomena, potentially reflecting reversible neuronal/synaptic dysfunction in the acute phase of the illness rather than neuronal degeneration.

[Isolated metamorphopsia and visual pseudohallucinations in a patient with anti-NMDA receptor encephalitis]

This article reports the case of a 40-year-old male patient with isolated metamorphopsia and visual pseudohallucinations lasting for 2 weeks. As the ophthalmological findings were not pathological, a further neurological examination was performed. After diagnosis of anti-N-methyl-D-aspartate (NMDA) receptor encephalitis, which can be manifested in various psychiatric, neurological and ophthalmological ways, the oligosymptomatic patient received high-dose corticosteroid treatment with intravenous immunoglobulins, which stopped the symptoms.

Transient Dyschromatopsia, Static Form Agnosia, and Prosopagnosia Observed in a Patient with Anti-NMDA Receptor Encephalitis

We presented a case of a 19-year-old woman who suffered from anti-N-methyl-D-aspartate (NMDA) receptor encephalitis associated with ovarian teratoma. The patient showed a variety of higher visual symptoms which changed over the recovery phase of the disease. In chronological order, she experienced cortical blindness, amblyopia, dyschromatopsia, static form agnosia, and prosopagnosia. Among these symptoms, the most intriguing was the static form agnosia. Although she could recognize the forms of moving objects, she could not make out those of stationary ones. All of these visual symptoms were transient, implying that she might have incidentally regained the function of the distinct cortical visual areas in the time course of follow-up. This case further suggests that visual functions concerned with the perceptions of static form and form-from-motion could be dissociable and may rely on distinct brain regions.

Tests of whole upright face processing in prosopagnosia: A literature review

Prosopagnosia refers to an acquired or developmental deficit in face recognition. This neuropsychological impairment has received increasing attention over the last decade, in particular because of an increased scientific interest in developmental prosopagnosia. Studies investigating prosopagnosia have used a variety of different clinical and experimental tests to assess face processing abilities. With such a large variety of assessment methods available, test selection can be challenging. Some previous works have aimed to provide an overview of tests used to diagnose prosopagnosia. However, no overview that is based on a structured review of the literature is available. We review the literature to identify tests that have been used to assess the processing of whole upright faces in acquired and developmental prosopagnosia over the last five years (2013-2017). We not only review tests that have been used for diagnostic purposes, but also tests that have been used for experimental purposes. Tests are categorised according to i) their experimental designs and, ii) the stage of face processing that they assess. On this basis, we discuss considerations regarding test designs for future studies. A visual illustration providing a structured overview of paradigms available for testing the processing of whole upright faces is provided. This visual illustration can be used to inform test selection when designing a study and to apply a structured approach to interpreting findings from the literature. The different approaches to assessment of face processing in prosopagnosia have been necessary and fruitful in generating data and hypotheses about the cause of face processing deficits. However, impairments at different levels of face processing have often been interpreted as reflecting a deficit in the recognition stage of face processing. Based on the data now available on prosopagnosia, we advocate for a more structured approach to assessment, which may facilitate a better understanding of the key deficits in prosopagnosia and of the level(s) of face processing that are impaired.

Visual dysfunction, but not retinal thinning, following anti-NMDA receptor encephalitis

Objective:

To assess structural and functional changes in the afferent visual system following anti-NMDA receptor (NMDAR) encephalitis.

Methods:

In this cross-sectional study including 31 patients after acute NMDAR encephalitis and matched healthy controls, visual function was assessed as high-contrast visual acuity using Early Treatment Diabetic Retinopathy Study charts and low-contrast sensitivity using Functional Acuity Contrast Test. Retinal changes were measured using optical coherence tomography with assessment of peripapillary retinal nerve fiber layer (pRNFL) and macular intraretinal layer thicknesses. Residual clinical impairment was described using the modified Rankin Scale.

Results:

High-contrast (logMAR 0.02 ± 0.14 vs −0.09 ± 0.14, p < 0.001) and low-contrast (area under the curve 1.89 ± 0.21 vs 2.00 ± 0.26, p = 0.039) visual acuity were reduced in patients in comparison to healthy controls. More severely affected patients performed worse in visual acuity testing than patients with good recovery (logMAR −0.02 ± 0.11 vs 0.08 ± 0.17, p = 0.030). In contrast, patients did not differ from matched healthy controls in pRNFL or in thickness of intraretinal layers, including the ganglion cell complex, the inner nuclear layer, the outer nuclear and plexiform layers, and the photoreceptor layer.

Conclusions:

After acute NMDAR encephalitis, patients have mild visual dysfunction in comparison to matched healthy controls, while retinal structure appears unaltered. These observations could point to an impairment of anterior or posterior visual pathway NMDAR function that is similar to dysfunction of NMDAR in cerebral cortex and subcortical structures. Alternatively, residual cognitive impairment might reduce visual function.