This population-based study evaluated the incidence and etiology of isolated, presumed fourth nerve palsy.

Study design

The authors used a database of Olmsted County, Minnesota, residents to identify all cases of isolated fourth nerve palsy diagnosed over a 15-year period.

Outcomes

Seventy-three patients were identified; mean age at presentation was 41.8 years. After adjustment for age and sex, the annual incidence rate was 5.73 per 100,000 per year, with a higher incidence in males than females.

The most common etiology was presumed congenital (49%), followed by hypertension (18%), and trauma (18%). One patient (1%) had fourth nerve palsy owing to a known intracranial neoplasm. The cause was undetermined for 3 patients (4%).

The most common decade of presentation was the fourth decade, including for presumed congenital cases.

Limitations

The population studied was predominately white. Thus, the results may be different for a more diverse population.

Clinical significance

This is an important review because it highlights the different etiologies of fourth cranial palsies. The findings further support that a vasculopathic etiology is just as common as head trauma, and in no case was an isolated fourth nerve palsy the presenting sign of an intracranial tumor.