Differential Diagnosis for Neurological Deficit with Inability to Look Laterally for a Long Time

• Single most likely diagnosis:
  • Sixth cranial nerve (abducens nerve) palsy: This condition affects the nerve responsible for controlling the lateral rectus muscle, which enables outward gaze. A palsy of this nerve would directly impair the ability to look laterally, making it a prime suspect for the described symptom.
• Other Likely diagnoses:
  • Third cranial nerve (oculomotor nerve) palsy with involvement of the lateral rectus muscle: Although the third cranial nerve primarily controls other eye movements, its dysfunction can indirectly affect lateral gaze due to the complex interactions between cranial nerves controlling eye movements.
  • Thyroid ophthalmopathy: This condition can cause inflammation and swelling of the tissues around the eye, including the muscles, which might restrict eye movement, including lateral gaze.
  • Orbital myositis: Inflammation of the eye muscles can restrict eye movement, potentially causing difficulty in looking laterally.
• Do Not Miss diagnoses:
  • Stroke or cerebral vasculitis: Although less directly related to the specific symptom of lateral gaze palsy, these conditions can cause a wide range of neurological deficits, including those affecting cranial nerves. Missing a stroke or vasculitis could have severe consequences.
  • Multiple sclerosis: This autoimmune disease can affect any part of the central nervous system, including the brainstem where cranial nerves originate, potentially causing a variety of neurological symptoms, including those affecting eye movement.
  • Tumors (e.g., brainstem glioma, acoustic neuroma): Tumors in strategic locations can compress or invade cranial nerves, leading to specific deficits like the inability to look laterally.
• Rare diagnoses:
  • Moebius syndrome: A rare neurological disorder characterized by facial paralysis and impaired eye movement, often including lateral gaze palsy.
  • Duane syndrome: A congenital disorder affecting the extraocular muscles, which can limit eye movement, including lateral gaze.
  • Gradenigo syndrome: A rare condition involving inflammation of the petrous apex of the temporal bone, which can lead to a combination of symptoms including lateral rectus palsy due to involvement of the sixth cranial nerve.