What causes positional vertigo, particularly in older adults over 50?

Causes of Positional Vertigo

Positional vertigo is most commonly caused by dislodged calcium carbonate crystals (otoconia) that break free from the utricle and migrate into the semicircular canals of the inner ear, creating benign paroxysmal positional vertigo (BPPV). 1, 2

Primary Mechanism: Displaced Otoconia

The fundamental cause involves otoconia—tiny calcium carbonate crystals normally anchored in the utricle—becoming "unglued" and floating into the semicircular canals. 1 This displacement occurs through two distinct mechanisms:

• Canalithiasis (most common): Free-floating otoconia move within the semicircular canal, creating inertial forces that abnormally stimulate the vestibular apparatus when the head changes position 1, 3
• Cupulolithiasis: Otoconial debris adheres directly to the cupula of the semicircular canal, causing abnormal stimulation 1

Canal Distribution

The posterior semicircular canal is affected in 85-95% of BPPV cases, while the lateral (horizontal) canal accounts for 5-15% of cases. 1 Anterior canal and multicanal variants are rare. 1

Risk Factors and Associated Conditions

Most cases occur spontaneously without identifiable cause, particularly in adults aged 50-70 years. 1, 4 However, specific risk factors include:

• Age: BPPV is significantly more common in older adults over 50 1, 4
• Head trauma: The most common cause in younger individuals 4
• Prolonged bed rest: Extended supine positioning or preferred sleep side 1
• Inner ear disorders: Pre-existing vestibular conditions 1
• Metabolic conditions: Diabetes and osteoporosis 1
• Migraine: Associated with vestibular migraine overlap 1
• Post-surgical: Following ear or mastoid procedures 1

Important Clinical Distinctions

BPPV must be differentiated from central causes of positional vertigo, which are less common but potentially dangerous. 1 Central causes include:

• Vestibular migraine: Distinguished by episodes lasting 5 minutes to 72 hours with migraine features (photophobia, phonophobia, aura), affecting 14% of vertigo cases 1
• Posterior circulation stroke: Particularly cerebellar stroke, which presented similarly to peripheral vertigo in 10% of cases in one series 1
• Multiple sclerosis and demyelinating disorders 1

Red Flags Suggesting Non-BPPV Causes

Atypical features that should raise concern for alternative diagnoses include:

• Downbeating nystagmus without torsional component on Dix-Hallpike testing 1
• Direction-changing nystagmus without head position changes 1
• Constant severe dizziness unaffected by position 1, 5
• Associated hearing loss 1, 5
• Syncope/fainting 1, 5
• Failure to respond to canalith repositioning procedures 1
• Neurological signs (dysarthria, dysmetria, dysphagia, sensory/motor deficits) 1

Age-Specific Considerations in Older Adults

In patients over 50, BPPV carries additional clinical significance beyond the vertigo itself. 1 This population faces:

• 12-fold increased fall risk when symptomatic with dizziness 1
• Greater susceptibility to serious injury from falls 1
• Atypical presentations: May manifest as isolated instability with position changes rather than classic spinning vertigo 1
• Higher healthcare costs: Falls in older adults exceed $20 billion annually in the United States 1

Clinicians should assess older patients with BPPV for modifying factors including impaired mobility, CNS disorders, lack of home support, and increased fall risk. 1