Symptoms:

• Confusion, delirium
• Difficulty swallowing
• Double vision
• Muscle spasms in the face, arms, or legs
• Reduced alertness, drowsiness or sleepiness, lethargy, poor responses
• Reduced vision
• Speech changes, poor enunciation
• Weakness in the face, arms, or legs, usually affecting both sides of the body

Other possible symptoms include:

• Constipation
• Different size pupils in the eyes
• Hallucinations
• Hand tremor
• Uncontrollable eye movements

Signs and tests:

An examination may show:

• Abnormal reflexes
• Cranial nerve VI paralysis (see cranial mononeuropathy VI)
• Involvement of all four arms and legs (spastic quadriplegia)
• Loss of eye muscle control
• Weakness of the face, arms, and legs (upper motor neuron syndromes)

A head MRI scan would reveal an abnormality in the brainstem (pons). This is the main diagnostic test.

Other tests may include:

• Blood sodium levels and other blood tests
• Brainstem auditory evoked response (BAER)