Isolated abducens nerve palsy preceding infectious mononucleosis

Abstract

Isolated sixth cranial nerve palsy is a neurological symptom of frequently unknown etiology in spite of extensive diagnostic procedures. In contrast to adults where other causes prevail, the underlying cause for this symptom in children is more often an infectious disease process. A 12-year-old girl suffering from a unilateral isolated abducens nerve palsy as a heralding and major feature of infectious mononucleosis is described. Although involvement of the nervous system in infectious mononucleosis has been described frequently, isolated sixth cranial nerve palsy is a quite unusual neurological complication, only three cases of which are reported in the scientific literature. As infectious mononucleosis has a high incidence in patients below 20 years of age and is characterized by a large variability of symptoms and clinical course, any unknown manifestation of abducens nerve palsy in children or adolescents should motivate a thorough search for signs of this disease. Since the usual clinical manifestations may be minimal or even absent and tests for heterophil antibodies are not necessarily positive, specific serological tests are of a high value for the differential diagnosis.