Objective:

To describe an atypical presentation of GQ1b antibody-associated syndrome manifesting as acute ophthalmoparesis without sensory ataxia, highlighting its diagnostic complexity and the importance of antibody testing.

Background:

GQ1b antibody syndrome encompasses a spectrum of disorders that include Miller Fisher syndrome, characterized by ophthalmoplegia, ataxia, and areflexia. However, incomplete or atypical forms may present with isolated cranial nerve involvement, often leading to misdiagnosis. Recognizing such variants is critical for accurate and timely management.

Design/Methods:

We report a single clinical case of acute ophthalmoparesis without ataxia, evaluated through neurological examination, neurophysiological testing, cerebrospinal fluid analysis, neuroimaging, and serological studies, including anti-GQ1b antibody testing.

Results:

A 32-year-old patient presented with an eight-day history of binocular horizontal diplopia that worsened with near vision and no prior similar episodes. Examination showed bilateral limitation of upward gaze, abduction, and left infraduction without ptosis or fatigability. Reflexes were globally decreased. Brain CT, MRI, and cerebrospinal fluid analysis were normal, as were neurophysiological studies and repetitive stimulation tests. Anti-GQ1b IgG antibodies were positive, confirming acute ophthalmoparesis without ataxia within the GQ1b antibody-associated spectrum.

Conclusions:

This case underscores the clinical variability of GQ1b antibody-associated syndromes. When typical Miller Fisher features are absent, antibody testing becomes decisive for diagnosis. Early recognition of atypical variants facilitates appropriate management and prevents unnecessary investigations.