A guide to the evaluation of fourth cranial nerve palsies

PURPOSE To devise a cost-effective guide for the evaluation of fourth nerve palsies (FNP). METHODS A review of the pertinent English language literature was performed to devise a guide for the evaluation (including neuroimaging) of FNP. The authors report a retrospective review of imaging studies performed on 206 patients with FNP. RESULTS The literature was used to develop the imaging guide. In the retrospective chart review of 206 patients from two tertiary care centers, 28 patients (13.6%) underwent a computed tomography scan and/or a magnetic resonance scan. Of these patients, five had associated neurological symptoms (non-isolated), one was traumatic, five were congenital, four were vasculopathic, eleven were non-vasculopathic, and two were progressive. Following the recommendations of the imaging guide, the five isolated congenital FNP and the four isolated vasculopathic FNP would not have undergone neuroimaging studies. The total costs of these neuroimaging studies in these nine patients were 19,000 dollars. Four patients in the retrospective review with associated neurological deficits (non-isolated) should have undergone neuroimaging according to the guide, but did not. CONCLUSIONS Although the evaluation of FNP can be difficult, the decision to order neuroimaging can be improved by using an imaging guide. An imaging guide for the evaluation of FNP may allow more appropriate and cost-effective imaging of these patients. Isolated congenital, old traumatic, or vasculopathic FNP do not require neuroimaging studies. Patients with non-isolated FNP should have directed neuroimaging studies based upon the results of clinical examination.