What is considered a forced deviation in the context of the National Institutes of Health (NIH) stroke scale?

From the Guidelines

A forced deviation in the context of the National Institutes of Health (NIH) stroke scale refers to a conjugate gaze abnormality where the patient's eyes are forcibly deviated to one side and cannot be overcome by voluntary or reflexive eye movements, receiving a score of 2 points in the gaze assessment section, indicating a severe deficit. This typically occurs when there is damage to the frontal eye fields or pontine gaze centers in the brain, causing the eyes to look toward the side of the brain lesion (and away from the side of body weakness) 1. On the NIH Stroke Scale, this finding is significant because it typically indicates a large hemispheric stroke and is associated with poorer outcomes. The NIHSS is an 11-part scale that measures the neurologic examination in a codified manner, with a score of less than 5 indicating a small stroke, and greater than 20 indicating a large stroke 1.

Some key points to consider when evaluating a patient with a suspected forced deviation include:

• The patient's level of consciousness, as assessed by the NIHSS, can impact their ability to follow commands and respond to stimuli 1
• The presence of other neurologic deficits, such as facial palsy, limb ataxia, or sensory disturbances, can help localize the area of brain damage 1
• The use of brain imaging studies, such as CT or MRI, is mandatory to distinguish ischemic stroke from hemorrhage or other structural brain lesions that may imitate stroke 1
• The severity of stroke, based on the findings detected by neurological examination, is a strong indicator of prognosis, with higher NIHSS scores associated with poorer outcomes 1

When evaluating a stroke patient, it's essential to distinguish forced deviation from a patient's inattention to one side or simple gaze preference that can be overcome. This can be done by assessing the patient's ability to follow commands, respond to stimuli, and move their eyes voluntarily or reflexively 1. By quickly and accurately assessing stroke severity and localizing the area of brain damage, clinicians can provide timely and effective treatment, improving patient outcomes.

From the Research

Definition of Forced Deviation

A forced deviation in the context of the National Institutes of Health (NIH) stroke scale refers to a condition where a patient's eyes are deviated to one side and cannot be moved to the midline or to the other side due to a neurological deficit.

Characteristics of Forced Deviation

• It is classified according to the National Institute of Health Stroke Scale (NIHSS) item "gaze palsy" as being forced, partial, or absent 2.
• Forced deviation is associated with higher initial NIHSS scores compared with patients without conjugate eye deviation (CED) 2.
• The presence of forced deviation on CT examination of acute ischemic stroke patients is associated with larger anterior circulation stroke volumes, higher risk of 24-hour hemorrhagic transformation, and 3-month disability or death 3.

Diagnosis and Assessment

• The NIH Stroke Scale is used to assess the severity of stroke and define candidates for thrombolytic treatment, but it requires specific training to use reliably 4.
• Conjugate eye deviation, including forced deviation, can be detected on admission CT images and is associated with higher admission NIHSS scores and larger middle cerebral artery territory infarct volume 3.
• The frequency of eye deviation, including forced deviation, is higher in stroke patients compared to non-stroke patients undergoing head CT 5.

Clinical Implications

• Forced deviation is a significant indicator of stroke severity and is associated with poor outcomes, including higher rates of disability or death at 3-month follow-up 3.
• The presence of forced deviation on CT examination can help identify patients at high risk of hemorrhagic transformation and poor outcomes, allowing for early intervention and management 3.