Can a concussion cause unilateral enlargement of the blind spot?

Can Concussion Cause Unilateral Enlargement of the Blind Spot?

Concussion can cause unilateral enlargement of the blind spot as part of the ocular-motor subtype of post-concussion syndrome, though this is not a common finding and requires careful evaluation to distinguish from other causes.

Ocular-Motor Dysfunction in Concussion

Concussion can lead to various visual disturbances through the ocular-motor subtype of post-concussion syndrome. According to the concussion guidelines, this subtype involves:

• Dysfunction of the visual system (eyesight, eye focusing, eye teaming, and visual perception skills) following injury 1
• Difficulty obtaining, understanding, and processing visual stimuli
• Deficits that may be detected through assessment of saccades, smooth pursuit, conjugate gaze, convergence, accommodation, and fixation

The ocular-motor subtype of concussion can manifest with several symptoms:

• Difficulty with visual activities (screen time, reading, near work, driving)
• Eye strain and eye fatigue
• Problems with visual focus
• Photophobia
• Blurred or double vision
• Frontal headaches or eye pain/pressure
• Vision-derived nausea
• Difficulty judging distances 1

Blind Spot Enlargement and Concussion

While blind spot enlargement is not specifically listed as a common finding after concussion in the guidelines, visual field defects can occur following traumatic brain injury. The connection between concussion and unilateral blind spot enlargement may involve:

1. Direct trauma to the optic nerve or peripapillary retina
2. Disruption of visual processing pathways
3. Secondary effects from increased intracranial pressure

Differential Diagnosis

It's important to distinguish concussion-related blind spot enlargement from other conditions that more commonly cause this finding:

1. Acute Idiopathic Blind Spot Enlargement Syndrome (AIBSES): Characterized by unilateral visual field loss in the blind spot area, acute onset photopsia, and few or no optic disc changes 2. This primarily affects young adults and is often misdiagnosed as optic neuritis.

2. Multiple Evanescent White Dot Syndrome: Can present with blind spot enlargement and is considered by some to be a subset of AIBSES 3.

3. Optic Nerve Disorders: Various conditions affecting the optic nerve can cause blind spot enlargement.

Evaluation of Visual Symptoms After Concussion

When evaluating a patient with suspected concussion and visual complaints:

1. Confirm binocular vs. monocular symptoms: Determine if the visual disturbance disappears when either eye is covered 4

2. Perform a thorough visual assessment:

   • Visual acuity testing
   • Ocular alignment in all positions of gaze
   • Smooth pursuit (visual tracking)
   • Saccades (visual fixation shifting)
   • Vestibulo-ocular reflex
   • Near point of convergence
   • Accommodation 5

3. Visual field testing: To document the extent of blind spot enlargement

4. Consider advanced imaging: MRI of the brain and orbits may be necessary to rule out structural causes if symptoms persist beyond the expected recovery period

Management Approach

For patients with concussion and visual symptoms including blind spot enlargement:

1. Initial management:

   • Rest and gradual return to activities
   • Avoidance of visual strain
   • Temporary accommodations for reading and screen time

2. Monitoring:

   • Most visual symptoms resolve spontaneously within 4 weeks 5
   • Regular follow-up to track resolution of symptoms

3. Referral indications:

   • Persistent symptoms beyond 4 weeks
   • Severe visual disturbances affecting daily functioning
   • Progressive worsening of symptoms

4. Specialist consultation: Consider referral to specialists with experience in comprehensive concussion management (sports medicine, neurology, neuropsychology, physiatry, ophthalmology) for additional assessment and treatment 5

Prognosis

The prognosis for visual disturbances following concussion is generally favorable:

• Most children and adolescents with visual symptoms after concussion recover spontaneously by 4 weeks 5
• A subset of patients may have persistent symptoms requiring specialized intervention
• Early identification and appropriate management may mitigate negative effects on quality of life

Conclusion

While unilateral enlargement of the blind spot is not among the most common visual findings after concussion, it can occur as part of the ocular-motor subtype of post-concussion syndrome. Careful evaluation is needed to distinguish this from other causes of blind spot enlargement, particularly AIBSES and other retinal or optic nerve disorders.