In the National Institutes of Health (NIH) stroke scale, does a negative visual threat test indicate complete hemianopia?

Understanding Visual Threat Testing in the NIH Stroke Scale

Yes, in the NIH Stroke Scale, a negative visual threat test indicates complete hemianopia. 1

Visual Field Assessment in the NIHSS

The NIH Stroke Scale (NIHSS) is a standardized assessment tool used to evaluate the severity of neurological deficits in stroke patients. Item #3 on the scale specifically assesses visual fields:

• Visual fields are scored on a 0-3 scale where:

  • 0 = no visual field defect
  • 1 = partial hemianopia
  • 2 = complete hemianopia
  • 3 = bilateral hemianopia 1

• The visual threat test is specifically used when patients cannot cooperate with formal visual field testing due to aphasia, confusion, or decreased level of consciousness 1

Visual Threat Testing Technique

When performing the visual threat test:

• The examiner brings their finger toward the patient's eye from the periphery on each side 1
• A normal response is for the patient to blink when the finger approaches from either side 1
• If the patient consistently fails to blink when the finger approaches from one side (negative visual threat response), this indicates a complete hemianopia (score of 2) on that side 1

Clinical Significance and Implications

Complete hemianopia has significant implications for patient outcomes:

• It indicates damage to the visual pathway, often from occipital lobe stroke or other posterior circulation lesions 1

• Patients with complete hemianopia experience:

  • Reduced vision-specific quality of life 2
  • Difficulties with mobility and navigation 1, 2
  • Challenges with reading, driving, and social functioning 2, 3
  • Increased risk of falls and injuries 3

• The presence of complete hemianopia contributes to the overall NIHSS score, which is a strong predictor of stroke outcomes:

  • Higher NIHSS scores (>20) correlate with poorer outcomes and higher risk of hemorrhagic transformation with thrombolytic treatment 1

Recovery and Rehabilitation

For patients with complete hemianopia:

• Some spontaneous recovery may occur within the first few months post-stroke, but many patients have permanent deficits 4, 3

• Early intervention is critical - visual function may be preserved in the subacute period but can deteriorate if not addressed 5

• Rehabilitation options include:

  • Compensatory scanning strategies and visual search training 1, 6
  • Prismatic correction to expand the visual field 3
  • Occupational therapy focused on adaptation to visual field loss 1
  • Mobility training to improve navigation abilities 2, 6

• Predictors of better adaptation to hemianopia include:

  • Preservation of the inferior visual field 6
  • Better performance on mobility assessment courses 6
  • Earlier initiation of visual rehabilitation 5

Common Pitfalls in Assessment

• Failure to distinguish between hemianopia and visual neglect, which can co-exist but require different rehabilitation approaches 1
• Not recognizing that patients may be unaware of their visual field defect 1
• Assuming visual deficits will spontaneously resolve without intervention 5, 3
• Delaying rehabilitation until the chronic phase, when earlier intervention shows better outcomes 5