Abstract
Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) represents a brief headache syndrome first described in 1989. Its name summarizes the clinical features: short-lasting, unilateral, neuralgiform headache attacks, with conjunctival injection, tearing and rhinorrhoea (1).
Although usually occurring without demonstrable structural abnormalities, a small number of potentially symptomatic cases of SUNCT syndrome have been reported with pathologies of the cerebellopontine angle (2–4), brain stem (5–7) and cavernous sinus (4, 8). Additionally, the relationship between SUNCT syndrome and trigeminal neuralgia is an interesting clinical question and an important physiological issue in the literature (9).
We describe a symptomatic case of SUNCT syndrome with compression of the trigeminal nerve by the anterior inferior cerebellar artery in the prepontine cistern. To our knowledge, this has not been previously described.
Case report
A 50-year-old male had pain attacks in the left orbital and periorbital area lasting 20–30 s for 2 years. He stated that he used to have three to four attacks per day, appearing as a group in earlier times; later the attack frequency increased to approximately 15–25 per day, coming in five to six groups. The onset of pain was quickly progressive, and its intensity varied from moderate to excruciating and burning or stabbing in quality. He also described a period lasting 2 days with 150–200 attacks per day. The attacks were dispersed during the day time. During all attacks he described conjunctival injection, tearing, nasal stuffiness and facial sweating. The attacks were spontaneous or most of the time on stimulation of trigeminal nerve-innervated areas by tooth brushing, eating and shaving.
Neurological examination of the patient was normal including sensation of the face. On physical examination, minimal oedema at the left periorbital area and minimal hyperaemia on left conjunctiva were observed.
Magnetic resonance imaging (MRI) of the patient revealed compression of the left trigeminal nerve by the anterior inferior cerebellar artery in the prepontine cistern (Fig. 1). Biochemical and hormonal evaluations, routine electrocardiography and chest X-ray examination were within normal limits.
Compression of left trigeminal nerve by anterior inferior cerebellar artery in prepontine cistern on axial MR image, 1: Left anterior inferior cerebellar artery, 2: Left trigeminal nerve.
The patient received no benefit from treatment with carbamazepine (800 mg/day), oxcarbamazepine (1800 mg/day), topiramate (150 mg/day), lamotrigine (400 mg/day), sertraline (100 mg/day), indomethasine (100 mg/day) or gabapentin (1200 mg/day).
Discussion
We describe a case of SUNCT syndrome sharing some features with trigeminal neuralgia, such as precipitation of pain on stimulation of the trigger areas and association with vascular compression of the trigeminal nerve, which is one of the most common causes of trigeminal neuralgia (10, 11). The anterior inferior cerebellar artery, which has been reported to be in part responsible for the compression of the trigeminal nerve(12–15), is involved in the case.
The relationship between SUNCT syndrome and trigeminal neuralgia is an interesting clinical and very important physiological issue (9). Sjaastad et al. (16) have commented on the distinction between SUNCT syndrome and trigeminal neuralgia by reporting the characteristics of first division trigeminal neuralgia, accepting some degree of autonomic activation. They concluded that the autonomic signs in V1 trigeminal neuralgia occurred in the later stages of disease and during particularly severe and long-lasting attacks.
Bouhassira et al. (17) and Sesso et al. (18), defining their cases seperately, thought that SUNCT syndrome may be a modified trigeminal neuralgia, characterized by more painful episodes, capable of triggering concomitant autonomous phenomena, suggesting just a single pathological condition, probably trigeminal neuralgia with autonomic features. They also suggested that every patient with diagnosed SUNCT syndrome should be carefully investigated for the absence of autonomic signs at the initiation of the algic condition. In our case, because of the possible unreliability of the symptomatology of the earlier attack, we can not decide if there is a transformation from trigeminal neuralgia.
The cranial symptoms observed in SUNCT syndrome have been proposed to be caused by activation of the trigeminal-autonomic reflex (19). In experimental head pain from capsacin injection (20) and in other forms of secondary trigeminal neuropathic pain (21), lacrimation has been observed. There is considerable literature on animal experiments to show that stimulation of trigeminal afferents can result in cranial autonomic outflow, the trigeminal autonomic reflex (19). It is concluded that some degree of cranial parasympathetic activation is a normal physiological response to nociceptive input in the first division of the trigeminal nerve (9).
If it is accepted that nociceptive input in the first division of the trigeminal nerve results in some degree of cranial parasympathetic activation, perhaps often subclinical, then one would expect to see such symptoms in trigeminal neuralgia (9). Indeed, these symptoms are sometimes seen in migraine (22). It is suggested that the key feature of trigeminal autonomic syndromes, such as SUNCT syndrome, is the degree, not the presence, of cranial autonomic activation (9).
In the second edition of the International Headache Society (IHS) diagnostic criteria, SUNCT syndrome appears in the section on ‘Cluster headache and other trigeminal autonomic cephalalgias’. These syndromes share the pathophysiological feature of pronounced activation of the cranial parasympathetic autonomic outflow in association with the pain (19). However, the current classification of SUNCT syndrome has some notable problems. First, the name implies that all patients must have both conjunctival injection and tearing. This is not the invariable clinical experience of the Headache Classification Subcommittee. It is possible that SUNCT is a subtype of a broader problem of SUNA (short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms). This proposal requires validation (23). The proposed criteria for SUNA allow pain accompaniments other than conjunctival injection and/or lacrimation such as nasal congestion, rhinorrhoea and eyelid oedema. Considering all of these, our case seems to be better described by the proposed term, SUNA.
SUNCT syndrome has a central pathogenesis rather than a peripheral vasculitic cause, with parasympathetic symptoms as manifestations of the trigeminovascular reflex (24, 25). In a functional MRI study, May et al. revealed significant activation in the region of the ipsilateral posterior hypothalamus (26). SUNCT syndrome is considered to be in primary headache category, but it has been described in some patients with pathologies of the cerebellopontine angle (2–4), brain stem (5, 6), cavernous sinus (4, 8) or with prolactinomas (27). Although trigeminal neuralgia and SUNCT syndrome are thought to be related, to our knowledge there is no reported case of this syndrome associated with trigeminal nerve compression.
The case seems to strenghten thoughts about a relationship between SUNCT syndrome and trigeminal neuralgia. In diagnostic evaluations of SUNCT syndrome, this relationship necessitates searching of the numerical aetiological pathologies of trigeminal neuralgia in addition to its own causal pathologies. Likewise, when evaluating MRI, neurovascular contacts causing trigeminal neuralgia should not be overlooked.