The diagnosis of idiopathic or “classical” TN is based mainly on the clinical history of pain attacks according to the International Classification of Headache Disorders [ICHD, 3rd edition (beta version)] criteria, together with a neurological exam and imaging studies. Symptomatic or secondary TN has to be excluded on the first place. Thorough head and neck examination should be performed, ruling out any dysfunction of the cranial nerves. A special attention deserves not only the trigeminal nerve (V) but also the facial (VII) and vestibulocochlear nerve (VIII), which lie adjacent to the trigeminal nerve in the cerebellopontine angle (CPA). If a symptomatic TN with involvement of the CPA is present, a subtle facial weakness and hearing loss on that side will be found. Hemifacial spasm may also occur.

Diagnostic brain imaging should be part of the initial diagnostic algorithm of any patient with TN symptoms. Landmarks around the trigeminal ganglion and the CPA are visualized. Although a routine brain computer tomography (CT) scan is usually sufficient for screening for a CPA tumor, it may not show small tumors, and the examination carries an appreciable dose of ionizing radiation. MRI has better sensitivity in the detection of intracranial lesions and improved definition and avoids ionizing radiation. Some authors recommend MRI of patients with trigeminal neuralgia as a routine consideration during their assessment. MRI imaging often demonstrates MS plaques better and the anatomic relationships of the trigeminal root.

We describe a clinical case of a 45-year-old woman, presenting initially with a typical first branch trigeminal neuralgia, who after 4 years of onset, started experiencing lacrimation on the affected side during the most severe attacks. No other accompanying autonomic symptoms were observed. Neurological, laboratory, and imaging exams were all normal before and after lacrimation had occurred. She did not have any past medical history, neither positive family history for multiple sclerosis, vasculitis, hypertension, etc. Carbamazepine 600 mg/daily was controlling well the symptoms until the clinical presentation of her TN changed. The primary diagnosis of “classical” TN was questioned because of the appearance of autonomic features, typical for TACs. Finally, we accepted the fact that our patient’s V1 TN was following its natural course, because mild autonomic signs like lacrimation may appear during severe attacks and after suffering for years from this disorder.

TN causes sudden, usually unilateral, severe brief, sharp electric-shock type recurrent pains in the distribution of one or more branches of the trigeminal nerve. Pain attacks start and terminate abruptly, and they can be evoked by trivial stimuli. Around 60 % of the patients with TN have the mandibular division of the trigeminal nerve involved, V3-TN. Only 30 % of the patients present with V2-maxillary division involvement. And less than 5 % of the patients experience involvement of V1-ophthalmic branch.

TN has an incidence of approximately 4/100,000. Although familial cases are reported, the majority of cases occur spontaneously, and TN does not appear to be more common in any ethnic group, geographic region, or climate. TN occurs in both genders, with a slight female predominance. TN is most common over the age of 50. TN may be idiopathic, “classical” (the majority of patients), or “symptomatic,” secondary to another disease process affecting the trigeminal system. Although the underlying mechanism of TN remains partially unknown, the effects of direct stimulation by closely located blood vessels are the most common related abnormalities. Benign tumors and vascular anomalies that compress the trigeminal nerve root can produce symptoms clinically indistinguishable from classical TN. Injury to the nerve root is a suggested initiating factor in the disease. It has been reported that TN in younger patients can be due to MS (demyelination in the root entry zone, the pontine tract, or the nuclei), tumors, aneurysms, angiomas, or vascular malformations. Diabetes mellitus is also proven to be a causative factor for TN, for which family history and blood sugar levels should be examined. TN may result also from infarction of the root entry zone of the trigeminal nerve and pons.