Man presents with visual field changes over 1 year
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A 66-year-old man was seen in the glaucoma clinic at Tufts Medical Center due to visual field changes, referred to neurology and then to neuro-ophthalmology with gradual left-sided peripheral visual field haziness over the past year.
He had no history of head or ocular trauma, no central visual changes, and no numbness, dizziness, tingling, slurring of speech, weakness or other neurologic signs. He said his memory had always been sharp; however, over the past several months, he had been more forgetful. MRI of the brain was obtained by neurology and was negative for an acute underlying etiology. A MoCA test was also performed during his neurology appointment.
Medical history was significant for hypertension. Ocular history was notable for low-risk glaucoma suspect, dry eyes, bilateral epiretinal membrane and asteroid hyalosis of the right eye. His medications included hydrochlorothiazide, lisinopril, amlodipine and artificial tears.
Examination
On examination, uncorrected visual acuity was 20/40 in the right eye and 20/50 in the left eye, with no improvement with pinhole. Pupillary examination was unremarkable with no relative afferent pupillary defect noted in either eye. IOPs were 20 mm Hg and 21 mm Hg in the right and left eyes, respectively, measured with Goldmann applanation tonometry. Extraocular motility was full and painless, and the patient was orthophoric.
Anterior segment examination noted 1+ meibomian gland dysfunction, trace conjunctivochalasis, trace punctate epithelial erosions, an irregular tear film, arcus, posterior chamber IOL and open posterior capsules bilaterally. Fundus examination noted trace asteroid hyalosis in the right eye, clear vitreous in the left eye, small cup-to-disc ratios bilaterally (0.4 right eye, 0.35 left eye) with peripapillary atrophy and slightly tilted discs, mild bilateral epiretinal membrane, and benign vasculature and peripheral examination.
Workup and management
Humphrey visual fields 30-2 were obtained in the clinic and noted a left homonymous hemianopia (Figure 1). OCT of the optic nerve was obtained but did not note any retinal nerve fiber layer (RNFL) thinning (Figure 2), particularly in the nasal and temporal fibers of the left and right eyes, respectively, which would correspond with the pattern of visual field loss. MRI of the brain was obtained by neurology and noted occipital lobe atrophy and no evidence of acute or chronic stroke, tumor or mass effect (Figure 3).
Source: Nisha S. Dhawlikar, MD, MPH, and Yosbelkys Martin Paez, MD
Recommended workup in this setting included the Cookie Theft picture (Figure 4a), Navon letters (Figure 4b) and the MoCA test (Figure 5). When shown the Cookie Theft picture, the patient was able to describe it appropriately. When examining the Navon letters, he was able to identify only the little F and L letters, not the overall H and F patterns. He scored poorly on the MoCA test at 18/30. No optic or oculomotor apraxia was noted.
Blood work was obtained, including vitamin B12, folate, complete blood count with differential, thyroid-stimulating hormone, Hashimoto’s antibodies, erythrocyte sedimentation rate, C-reactive protein and antinuclear antibody, and all were within normal limits.
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Visual field changes
Given the patient’s left-sided visual field changes with memory difficulty, the top differential to rule out was a right-sided stroke or post-chiasmal structural lesions such as an arteriovenous malformation or cavernous malformation. However, it would be atypical for these diagnoses to present gradually and without other neurologic signs, although occipital cortex strokes can be subclinical. These diagnoses also would not explain the cognitive impairment findings on his MoCA test. Neurodegenerative disorders such as Benson’s disease or posterior cortical atrophy must be considered in a patient presenting with forgetfulness and trouble with visuospatial tasks. Posterior cortical atrophy can present similarly to Alzheimer’s disease with memory and visuospatial difficulty, and it is oftentimes a delayed diagnosis due to the younger age of presentation.
The patient’s visual processing deficits in conjunction with his cognitive impairment, left homonymous hemianopia of unclear chronicity and MRI head findings of occipital lobe atrophy made posterior cortical atrophy the most likely diagnosis.
Discussion
Posterior cortical atrophy (PCA) is a neurodegenerative condition that often goes underdiagnosed for many years due to its atypical presentation. Age of onset is typically 50 to 65 years, and it is characterized by a progressive decline in visual spatial function. PCA can affect the parietal, occipital and occipitotemporal cortices, and under-recognition of this condition leads to a considerable delay in diagnosis due to the younger age of presentation compared with Alzheimer’s disease and dementia with Lewy bodies.
PCA is oftentimes thought of as the visual variant of Alzheimer’s disease due to the deficits in visuospatial tasks and higher-order visual functions. Thus, ophthalmologists may be one of the first physicians sought out in patients with this disease due to progressive visual disturbance. As described by Balint, a clinical triad occurs secondary to a bilateral parieto-occipital lesion: optic ataxia, oculomotor apraxia and simultanagnosia. Optic ataxia is the inability to guide the hand toward an object using visual information in which the inability cannot be explained by motor, somatosensory, visual field or acuity deficits. Oculomotor apraxia is the inability to voluntarily shift gaze to an object of interest despite intact extraocular muscle function. Simultanagnosia is the prototype of visuospatial disorder in PCA, or the failure to perceive a visual scene as a whole, despite being able to see the individual elements. More awareness within the ophthalmology community is required to appropriately diagnose patients with PCA and refer them for further workup and management.
A variety of visual field deficits can be noted in PCA, with the most common being homonymous hemianopia. Kim and colleagues described a 56-year-old woman who presented with 1 year of visual disturbance and was found to have left homonymous hemianopia, left-sided visual extinction to double simultaneous stimuli and rightward deviation in neglect exams. A case series published in 2011 by Pelak and colleagues identified seven of nine patients with PCA and homonymous hemianopia or quadrantanopia and two patients with bilateral visual field constriction. Seven of the nine patients also had prominent difficulty with driving.
In patients with concern for PCA, MRI of the brain with and without contrast should be obtained. Atrophy in the parietal, occipital and occipitotemporal cortices can be identified. It is also important to establish them with a neurologist for a thorough neurocognitive evaluation and possible lumbar puncture to test for other neurocognitive diseases including Alzheimer’s disease, Lewy body dementia and prion disease.
Astute clinicians who identify possible neurocognitive dysfunction can perform some of the evaluation in the ophthalmology clinic itself. The Montreal Cognitive Assessment (MoCA) tests higher-order cognition including visuospatial or executive function, naming, memory, attention, language, abstraction, delayed recall and orientation. It is a screening test for mild cognitive impairment, and a score of 26/30 or higher indicates intact cognition. The patient in this case scored 18/30 on the MoCA test, indicating the presence of cognitive impairment, mainly involving visual spatial function. The MoCA test has been used as a screening tool and has low sensitivity for diagnosis of PCA. If scoring low on MoCA, patients should ideally undergo neuropsychological testing to identify which domain is affected. Hierarchical Navon letters, made of large “global” letters and small “local” letters, are used to identify global and local processing ability. Our patient was able to identify local letters F and L; however, he could not identify the global H or F, characteristic of simultanagnosia. The Cookie Theft picture test is a method of assessing language as the scene is complex and requires a detailed description. Through this picture, language skills are assessed including word frequency, content words, prepositions and pronouns to better quantify the level of aphasia. The patient in this case was able to describe the Cookie Theft picture appropriately and was not aphasic.
Although the patient had progressive left-sided visual complaints, his diagnosis was delayed at least 1 year. Visual field testing in clinic helped to quantify the field loss, and MRI of the head identified the PCA and ruled out acute pathology. The neurocognitive tests performed in the office shed more light to the level of this patient’s cognitive impairment. Thus, in middle-aged or older patients who present to the ophthalmology clinic with vague unidentified visual symptoms, formal visual field testing should be obtained to allow for the possible diagnosis of PCA.
Clinical course continued
A repeat MRI of the head with and without contrast was recommended to further evaluate posterior cortical regions; however, the patient declined this repeat imaging due to the costly co-pay. He was also advised against driving given the combination of his hemianopia and cognitive impairment. Neurology follow-up was scheduled for this patient for further workup. He will return for follow-up in the neuro-ophthalmic clinic in 3 months.
- References:
- Bálint R. Eur Neurol. 1909;25(1):51-66.
- Battaglia-Mayer A, et al. Brain. 2002;doi:10.1093/brain/awf034.
- Crutch SJ, et al. Lancet Neurol. 2012;doi:10.1016/S1474-4422(11)70289-7.
- Faroqi-Shah Y, et al. J Commun Disord. 2020;doi:10.1016/j.jcomdis.2020.105994.
- Kim CY, et al. Korean J Ophthalmol. 2019;doi:10.3341/kjo.2019.0014.
- Pelak VS, et al. Neurology. 2011;doi:10.1212/WNL.0b013e31823e9f2a.
- Wong B, et al. Neurodegener Dis Manag. 2019;doi:10.2217/nmt-2018-0052.
- For more information:
- Nisha S. Dhawlikar, MD, MPH, and Yosbelkys Martin Paez, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Allison V. Coombs, DO, MS, and Nisha S. Dhawlikar, MD, MPH. They can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.