Isolated trigeminal neuralgia as the presenting symptom of cerebellopontine infarction: a case report

Abstract

Trigeminal Neuralgia (TN) characteristically presents as unilateral recurring shock-like pain in the trajectory of the trigeminal nerve and its branches. Secondary TN is rare due to an ischemic lesion of the trigeminal root entry zone in pons. Here we report a patient with a cerebellopontine infarction transecting the central trigeminal pathways, resulting in isolated trigeminal neuralgia. A 72-year-old male patient presented to our emergency department with numbness and recurrent shock-like pain attacks on the left side of his face lasting 3 to 5 seconds starting abruptly 20 days ago and increasing in frequency in the last two days. Neurologic examination revealed slight hypoesthesia to touch on the left maxillary trigeminal nerve dermatome. There was no other abnormality in the neurological examination. In the initial work-up, Diffusion-Weighted Magnetic Resonance Imaging (MRI) showed hyperintensity on the junction of the pons and left inferior cerebellar peduncle, the root-entry-zone of the left trigeminal nerve, without hypointensity in Apparent Diffusion Coefficient (ADC) sequence. Noncontrasted Computer Tomography (CT) revealed hypodensity in the same region. After the admission, an MRI showed the lesion was T1-hypointense, T2-hyperintense, minimally heterogeneously IV gadolinium-contrast enhancing, consistent with subacute infarction. Secondary TN without any other abnormal neurologic signs attributed to an ischemic lesion of the trigeminal root entry zone in pons is unusual, but not impossible, and responds well to carbamazepine treatment. Patients who present with TN should undergo a comprehensive work-up to identify probable secondary matters.