Skew Deviation

Skew deviation is a vertical misalignment of the eyes caused by damage to parts of the brainstem or cerebellum that control vertical eye position. Unlike other causes of vertical double vision, skew deviation results from disruption of the vestibular (balance) pathways that help keep the eyes level.

Understanding Skew Deviation

The vestibular system helps keep your eyes level, even when your head tilts. Signals travel from the inner ear through the brainstem to the eye muscles. When this pathway is damaged, one eye may drift up or down relative to the other, causing the eyes to be vertically misaligned.

Symptoms

Primary Symptom

Vertical double vision

• One image appears above the other
• Present in most or all gaze directions
• May change with head position

Associated Symptoms

Depends on cause, but may include:

• Dizziness or vertigo
• Imbalance
• Head tilt
• Other brainstem symptoms (weakness, numbness, difficulty swallowing)
• Oscillopsia

Key Features

• Comitant (similar in all directions) or incomitant misalignment
• Often associated with head tilt
• Ocular torsion (eyes rotated)
• Associated with ocular tilt reaction

Causes

Brainstem Lesions

• Stroke (most common in elderly)
• Multiple sclerosis (common in young adults)
• Tumors
• Infection

Cerebellar Lesions

• Stroke
• Tumors
• Degenerative conditions

Peripheral Vestibular

• Inner ear disorders (less common cause)

Other

• Trauma
• Arnold-Chiari malformation
• Increased intracranial pressure

Diagnosis

Clinical Examination

Distinguish from fourth nerve palsy:

Feature	Skew Deviation	Fourth Nerve Palsy
Worse in downgaze	No	Yes
Hyperdeviation (which eye higher)	May alternate	Consistent
Head tilt	Toward lower eye	Away from affected eye
Ocular torsion	Toward lower eye	Toward higher eye
Other neuro findings	Often present	Usually absent

Imaging

MRI brain

• Essential to identify underlying lesion
• Focus on brainstem and cerebellum
• May reveal stroke, MS plaques, tumor

Vestibular Testing

• May be done to evaluate inner ear function
• Helps distinguish peripheral from central cause

Treatment

Treat Underlying Cause

• Stroke management
• MS treatment
• Tumor treatment
• Address any treatable condition

Manage Double Vision

Prism glasses

• Can be effective for stable skew deviation
• May need adjustment as condition changes

Patching

• Temporary measure for diplopia

Observation

• Some cases resolve as underlying condition improves
• Monitor for stability or change

Prognosis

Variable

• Depends on underlying cause
• Stroke-related may improve over time
• MS-related may resolve with treatment
• Some cases persist

Recovery Factors

• Time since onset
• Underlying cause and its treatment
• Extent of brainstem/cerebellar damage

Frequently Asked Questions

How is skew deviation different from other causes of double vision?

Skew deviation is a specific type of vertical misalignment caused by damage to vestibular pathways in the brainstem. Unlike fourth nerve palsy, which affects a specific eye muscle, skew deviation results from disordered vestibular control of eye position. The distinction matters because skew deviation usually indicates a brainstem problem.

Is skew deviation serious?

Skew deviation itself causes double vision, which is bothersome but not dangerous. However, it indicates a problem in the brainstem or cerebellum, which may be serious (like stroke). The underlying cause needs to be identified and treated.

Will my double vision go away?

Possibly. If the underlying cause improves (like recovery from stroke or treatment of MS), the skew deviation may resolve. In other cases, it may persist but can often be managed with prism glasses.

References