Diagnosis and Management of Left-Beating Nystagmus

Initial Diagnostic Assessment

The American Academy of Otolaryngology recommends performing systematic positional testing to characterize the nystagmus, including observing for spontaneous nystagmus in primary gaze, which suggests a central etiology requiring neuroimaging if present constantly without positional provocation 1
The American Academy of Otolaryngology suggests performing the supine roll test to assess for lateral semicircular canal BPPV by positioning the patient supine with head neutral, then quickly rotating the head 90° to each side while observing for nystagmus 2, 1
The American Academy of Otolaryngology recommends performing the Dix-Hallpike maneuver for each side to assess posterior canal involvement, looking for characteristic torsional upbeating nystagmus with latency and crescendo-decrescendo pattern 3

For horizontal left-beating nystagmus on supine roll test, a geotropic pattern (nystagmus beats toward the ground) indicates that the affected ear is the one that produces the most intense nystagmus when it is down 2, 1
An apogeotropic pattern (nystagmus beats toward the uppermost ear) suggests that the affected ear is typically opposite to the side with the strongest nystagmus 2

The American College of Radiology recommends immediately obtaining MRI of the brain if any of the following central features are present: downbeat component to the nystagmus without torsional features, pure vertical nystagmus (upbeat or downbeat) in primary gaze, nystagmus present in primary position without positional provocation, direction-changing nystagmus in primary gaze, or associated neurological signs 4
The American College of Radiology recommends MRI as the preferred imaging modality to identify structural lesions of the brainstem, cerebellum, or cervicomedullary junction 4

For geotropic lateral canal BPPV, the American Academy of Otolaryngology recommends performing canalith repositioning maneuvers (barbecue roll or Gufoni maneuver) directed toward the affected ear 2

The American Academy of Otolaryngology advises against assuming the side toward which head turning triggers vertigo is automatically the affected ear, and instead recommends systematic testing 2
The American Academy of Otolaryngology warns against misdiagnosing central causes as BPPV, and recommends careful evaluation for downbeat nystagmus without torsional component, direction-changing nystagmus in primary gaze, and baseline spontaneous nystagmus 4
The American Academy of Otolaryngology recommends exercising caution with positional testing in patients with cervical stenosis, limited cervical range of motion, severe kyphoscoliosis, cervical radiculopathies, ankylosing spondylitis, spinal cord injuries, or morbid obesity 2, 1