A negative electroretinogram (ERG) in a case of probable multiple system atrophy (MSA)

Area of Science:

• Neuro-ophthalmology
• Neurology
• Genetics

Background:

• Negative electroretinograms (ERGs) have been infrequently observed in patients with cerebellar degeneration.
• Previous cases were predominantly hereditary, with some linked to spinocerebellar ataxia-1 (SCA-1) gene mutations, while others were sporadic.

Observation:

• A 65-year-old man presented with a 5-year history of ataxia, autonomic dysfunction (orthostatic hypotension, bladder/erectile dysfunction), and mild visual impairment.
• Fundus examination revealed optic nerve pallor; visual fields showed enlarged blind spots.
• ERG testing demonstrated reduced and delayed rod b-waves, with b-waves smaller than a-waves, despite normal photopic responses.

Findings:

• Genetic testing excluded hereditary optic neuropathies and SCA gene expansions.
• This case represents the third reported instance of sporadic ataxia with a negative ERG.
• The patient's significant autonomic dysfunction met criteria for probable multiple system atrophy (MSA).

Implications:

• This case expands the differential diagnosis for negative ERGs in patients with ataxia.
• It suggests that the visual system may be affected in multiple system atrophy (MSA).
• Further research is warranted to understand the neurophysiological basis of visual disturbances in MSA.