A 36-year-old female dentist presented with acute right-sided visual field loss. She denied accompanying headache, ocular or neurologic symptoms. Ophthalmic examination revealed a right inferior homonymous quadrantanopia. Her ophthalmic and neurologic examinations were otherwise unremarkable. She had a history of hypermobile variant of Ehlers-Danlos syndrome according to clinical criteria. She had no prior history of migraine or head trauma and did not engage in smoking or substance use. Initial neuroimaging with a CT head was unrevealing. Brain MRI eleven days later demonstrated a hyperintense fluid-attenuated inversion recovery (FLAIR) lesion centered within the posterior limb of the left internal capsule and the posterior margin of the left optic tract, with slight extension into the posterior aspect of the globus pallidus (Figure 1A); CT angiography of the head and neck demonstrated a small focal dilatation of the V1 segment of the left vertebral artery, most consistent with left vertebral artery dissection (Figure 1B). In consultation with a stroke neurologist, she was started on acetylsalicylic acid 81 mg daily.

Figure 1.

(A) T2-FLAIR MRI image showing a hyperintense lesion centered within the posterior limb of the left internal capsule and the left optic tract. It demonstrated restricted diffusion (not shown), consistent with an acute infarct. (B) CTA image showing a small dilatation of the V1 segment of the left vertebral artery, consistent with dissection. CTA = CT angiography; FLAIR = fluid-attenuated inversion recovery.

Eighteen days following scotoma onset, the patient developed generalized constant flickering and pulsating “static” throughout her vision bilaterally, described as a sensation of “speckled vision” with red afterimages lasting minutes when her eyes were closed. This was accompanied by photophobia, palinopsia, tinnitus and self-limiting neck pain with occipital headache. Her symptoms were consistent with new-onset visual snow (VS)-like syndrome.

In the months following the stroke, there was gradual near-complete resolution of her right inferior quadrantanopia on perimetry. Optical coherence tomography of the macula showed a homonymous pattern of ganglion cell loss in the right nasal macula and left temporal macula (Figure 2), consistent with a left pre-geniculate lesion. The patient’s visual symptoms improved significantly over the following year, although she noticed persistent “pulsations” and “pixelation” when looking at uniform surfaces. Follow-up brain MRIs at 3, 9 and 30 months were stable.

Figure 2.

Optical coherence tomography of the macula showing homonymous ganglion cell layer loss in the right nasal macula and left temporal macula.

Figure 2. Long description

The OCT macular thickness profiles of the left and right eyes consist of colour-coded retinal thickness and GCL thickness maps in micrometers, retinal thickness and GCL thickness deviation maps, 6 sector grids of the macula, and an OCT B-scan across the fovea with labels distinguishing the RNFL and GCL layers. The GCL thickness profiles show thinning at the right nasal macula and left temporal macula. Abbreviations: GCL, ganglion cell layer; OCT, optical coherence tomography; RNFL, retinal nerve fiber layer.

VS syndrome is a clinical diagnosis in which patients experience a static-like or flickering visual disturbance across the entire visual field continuously for at least three months, in addition to at least two associated symptoms including palinopsia, photophobia, nyctalopia or enhanced entoptic phenomena. ^{Reference Schankin, Maniyar, Digre and Goadsby1} Ocular, retinal and neurologic causes such as migraine or seizure should be excluded before diagnosing VS syndrome.

An acute VS-like syndrome has been described in the setting of retinopathies or following neurologic disease such as neuro-trauma, concussion, infection or cortical disorders such as stroke, epilepsy, multiple sclerosis, neoplastic or neurodegenerative diseases. In our review of cases of acute VS-like syndrome with identifiable intracranial lesions, all involved pathways posterior to the lateral geniculate nucleus, most commonly the occipital lobe or temporal lobe, ^{Reference Mehta, Garza and Robertson2} or in association with glycine receptor antibody syndrome. ^{Reference Piquet, Khan and Warner3}

To our knowledge, this is the first reported case of new-onset VS-like syndrome developing following a lesion to the pre-geniculate visual pathway. Thalamic lesions may be associated with thalamic dazzle, which presents with painless photophobia and represents a rare central sensory dysfunction following ischemia involving the thalamus. However, our patient’s predominant symptoms included positive visual phenomena, afterimages and palinopsia in addition to photophobia, which are not described in thalamic dazzle and are more consistent with VS-like syndrome. ^{Reference Nakhleh, Charoenkijkajorn, Pakravan, Mortensen and Lee4}

The pathophysiology of VS syndrome is poorly understood. A leading theory, termed “thalamocortical dysrhythmia,” implicates a network disorder between cortical and pre-cortical areas involved in visual perception and processing. ^{Reference Aeschlimann, Klein and Schankin5} Thalamocortical dysrhythmia has been suggested to explain differences in regional metabolism and modulation of neuronal sensitivity, leading to altered connectivity between cortical and subcortical structures that are involved in visual stimuli post-processing, ^{Reference Klein and Schankin6} which is supported by the results of functional MRI. ^{Reference Puledda, O’Daly, Schankin, Ffytche, Williams and Goadsby7}

The present case raises the novel possibility that a delayed VS-like syndrome may occur following a lesion to the pre-geniculate visual pathway, possibly from disrupted visual input to the thalamus. We acknowledge that our patient’s lesion, while centered around the left optic tract, also involved the globus pallidus and could have extended to more posterior visual pathways which could have important alternative mechanistic implications. Our patient’s debilitating symptoms of VS improved significantly after one year which may represent a delayed network recalibration. ^{Reference Fraser8} We emphasize the concept that patients presenting with acute symptoms resembling VS-syndrome be strongly considered for neuroimaging of the pre- and post-geniculate visual pathways.