From the Guidelines
The Brainstem Functional System (FS) score for this patient would be 2, indicating moderate impairment of the brainstem function based on the patient's symptoms of diplopia on right lateral gaze and the clinical finding of mild limitation of abduction in the right eye. This score is determined by the patient's symptoms and clinical findings, which suggest a right cranial nerve VI (abducens nerve) palsy, affecting the lateral rectus muscle responsible for eye abduction 1. The Brainstem FS score is part of the Expanded Disability Status Scale (EDSS) used in multiple sclerosis assessment, where 0 represents normal function and higher scores indicate increasing disability.
Key Points to Consider
- A score of 2 reflects definite abnormality that is mild to moderate in severity but does not significantly impair daily function.
- This particular presentation is consistent with a partial sixth nerve palsy, which can result from lesions in the brainstem affecting the abducens nucleus or nerve fascicle, often seen in conditions like multiple sclerosis, stroke, or other inflammatory or vascular disorders affecting the brainstem 1.
- The patient's symptoms and clinical findings are consistent with the description of abducens palsy in the adult strabismus preferred practice pattern, which typically presents with an acute onset of horizontal double vision, worse at distance than at near and worse laterally toward the side of the affected nerve 1.
Clinical Implications
- The diagnosis of a sixth nerve palsy can be associated with various underlying pathologies, including vasculopathic, traumatic, and neoplastic causes 1.
- Further evaluation is necessary to determine the underlying cause of the sixth nerve palsy, especially if no recovery is apparent by 6 months, as approximately 40% of patients may demonstrate a serious underlying pathology warranting further evaluation 1.
From the Research
Brainstem FS Score
The Brainstem FS score is not directly mentioned in the provided studies. However, the patient's symptoms of diplopia on right lateral gaze and mild limitation of abduction in the right eye are indicative of a sixth cranial nerve palsy.
Sixth Cranial Nerve Palsy
- The studies suggest that sixth cranial nerve palsy can be caused by various factors, including multiple sclerosis 2, 3, 4, presumed inflammatory lesions 5, and presumed microvascular causes 5.
- In the case of multiple sclerosis, sixth cranial nerve palsy can be an initial presentation 4 or a subsequent symptom 2, 3.
- The diagnosis of sixth cranial nerve palsy is typically made through clinical assessment and imaging studies, such as MRI 2, 3, 5.
Relevance to Brainstem FS Score
- While the provided studies do not directly mention the Brainstem FS score, they do suggest that sixth cranial nerve palsy can be a symptom of underlying brainstem or central nervous system pathology 2, 3, 5, 4.
- Further evaluation and testing, including imaging studies and laboratory tests, may be necessary to determine the underlying cause of the sixth cranial nerve palsy and to assess for any associated brainstem or central nervous system involvement 2, 3, 5, 4.