What are the common neurologic features of hypothyroidism?
Hypothyroidism causes headache, fatigue, slowness of speech and thought, apathy, and inattention in 90% of patients and is often mistaken for early dysthymia or depression.
Reversible sensorineural hearing loss, with or without tinnitus, develops in 75% of hypothyroid patients, and reversible ptosis occurs in 60% of patients as a result of diminished sympathetic tone.
Sleep apnea occurs in up to half of hypothyroid patients and usually results from obstructive problems due to associated obesity and myxedema.
Seizures are reported in 20% of patients, often as the presenting neurologic sign. Prolonged relaxation time for deep tendon reflexes can be elicited in many hypothyroid patients but is not specific for the disease.
Rarely, hypothyroidism is associated with limb ataxia, nystagmus, carpal tunnel syndrome, demyelinating polyneuropathy, optic neuropathy, ophthalmoparesis, pseudotumor cerebri, trigeminal neuralgia, Bell’s palsy, reversible dementia, or overt psychosis (myxedema madness).
Myopathy in hypothyroidism is common and ranges between 30% and 80% of cases.
The major symptoms related are weakness, muscular cramps, and myalgia. The pseudohypertrophic form is called Hoffman’s syndrome.
Laboratory investigation shows increased levels of muscle enzymes, low serum thyroid hormones, and elevated thyrotropic-stimulating hormone.
