• Neuro-Ophthalmology/Orbit

    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.


    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.


    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.