Aneurysms involving the intrapetrous internal carotid artery: a rare cause of Horner's syndrome

Abstract

Aneurysms involving the intrapetrous carotid artery are a rare cause of Horner's syndrome and only three cases appear to have been described previously. These aneurysms vary in their mode of clinical and radiological presentation depending on the direction of expansion of their sac. Non-invasive radiological investigation may demonstrate striking abnormalities, but the definitive diagnosis can only be made by angiography. A 19-year-old woman who was 34 weeks pregnant complained of an attack of severe migrainous headache, which had left her with a drooping left eyelid. This attack was similar to many she had experienced since the age of 8 years, but none previously had been followed by neurological deficit. She gave no history of head injury or middle ear infection. Examination revealed left Horner's syndrome, in addition to partial left 8th, 9th and 10th cranial nerve palsies. All other tests were normal. Radiological investigation was deferred until she had delivered her baby. Plain radiographs of the skull base (Fig. 1) showed a large area of pressure erosion of the medial half of the floor of the left middle cranial fossa with a scalloped margin. Unenhanced axial computed tomographic (CT) sections defined a soft-tissue mass impressing the nasopharynx and obliterating the left fossa of Rosenmuller. Magnetic resonance imaging (MRI) confirmed the presence of a mass lesion eroding the base of the skull in region of the carotid canal (Fig. 2).