Headache and pain disorders constitute the leading causes of morbidity and disability in the world. There are many types of headache disorders that have been categorized by the International Classification of Headache Disorders. Short lasting unilateral neuralgiform headache is a type of trigeminal autonomic cephalalgia and occurs in a unilateral fashion that comes with some autonomic features. There are two kinds of unilateral neuralgiform headache: 1. Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) 2. Short-lasting unilateral neuralgiform headache with autonomic symptoms (SUNA) which will be described in detail in this article.
Although relatively rare, these headache attacks are easy to recognize, given their constellation of signs and symptoms. SUNCT and SUNA classify as part of the trigeminal autonomic cephalalgias (TACs). They are considered to be the headache with the most frequent attacks that range from 2 to 600 times daily, but averaging < 100/day. The attacks are usually of moderate to severe intensity and can have throbbing pain or sharp at times.
A Stimulus to the trigeminal nerve is required to start the cascade. The stimulus could be simple or a noxious one. Once the trigeminal ganglion is activated, it projects impulses to the trigeminal-cervical complex, which is composed of C1/C2 dorsal horns and the trigeminal nucleus caudalis (TNC). From the trigeminal-cervical complex neurons project to the superior salivary nucleus (SSN) in the pons, which sends parasympathetic fibers that synapse on the sphenopalatine ganglion. After synapsing at the ganglion, post-ganglionic parasympathetic fibers innervate the lacrimal gland and the nasal mucosa and palate.
The estimated prevalence of SUNCT and SUNA is 6.6 per 100,000, and the annual incidence to be 1.2 per 100,000. The age of onset typically is between 35 and 65 with a mean age of 48. There is a male predominance in SUNCT, while female predominance in SUNA, similar to trigeminal neuralgia. One recently published case report of a familial SUNCT syndrome.
The exact pathophysiology of SUNCT and SUNA remains unknown. Hypothalamic dysfunction has been reported in current research that leads to the overproduction of nociceptive orexin B that results in the trigeminal-hypothalamic tract, which activates the pain pathway. There is also a secondary activation of cortical areas that occur after the activation of the trigeminal-cervical complex, and this leads to the severe pain associated with this SUNCT and SUNA.Patients who underwent deep brain stimulation to the ventral tegmental area (VTA) ipsilateral to the side of the attacks showed about 80% improvement in symptoms; this finding supports the involvement of VTA in the pathophysiology of SUNCT and SUNA.
Pain in short-lasting unilateral neuralgiform headache is generally in the V1 distribution and can be described as sharp, stabbing, burning, or electrical shocks. Patients must report at least 20 attacks that fulfill the criteria for short-lasting unilateral neuralgiform headache. Attacks must be of moderate to severe pain intensity lasting 1-600 seconds with the orbital, supraorbital, or temporal distribution. These attacks must also be associated with at least one of the following autonomic symptoms: conjunctival injection, stuffy nose, tearing, rhinorrhea, eyelid swelling, increased sweating in the head and neck regions, or redness, ear discomfort, or miosis/ptosis.
Similar to trigeminal neuralgia, SUNCT and SUNA can also be triggered by external stimulus. Common triggers include any irritation of the trigeminal nerve such as chewing, touching the face, brushing teeth, temperature, or even loud noise. They are differentiated from trigeminal neuralgia by the presence of cranial autonomic symptoms. Although migraine and other types of facial pain can stimulate the parasympathetic ganglion and produce some autonomic symptoms, they will not be as pronounced as the ones with SUNCT and SUNA.
Because SUNCT/SUNA can be secondary or symptomatic of underlying structural pathology, including pituitary, posterior fossa, or local lesions, a brain MRI with pituitary views and blood tests for pituitary function must be the minimal work-up for SUNCT/SUNA.
However, the diagnosis is mostly clinical and is defined by the International Classification of Headache Disorders 3rd edition by the following diagnostic criteria.
A) Have had a minimum of 20 headache episodes that fulfill the criteria below
B) Headache is at least of moderate-intensity in the orbital or temporal area on one side and lasts more than one second but less than 600 seconds.
C) Must have one of the below symptoms on the same side as the headache
1. Tearing and redness of the eyes 2. Stuffy nose or runny nose3. Eyelid swelling on the same side as the headache 4. Sweating of head and neck area 5. Redness of head and neck area 6. Ear fullness and discomfort 7. Droopy eyelid or pinpoint pupil
D) At least one attack per day when the disease is active
These headache attacks occur very frequently when the disease is active. SUNCT and SUNA tend to have some associations with seasons.
There are three categories of treatment for trigeminal autonomic cephalalgia, including SUNCT and SUNA: acute, preventive, and bridge therapies.
Short Term Prevention
A trial of intravenous lidocaine reported some relief in patients with SUNCT and SUNA. Requires cardiac and blood pressure monitoring and, therefore, must be given in an intensive care unit (ICU) or other inpatient monitored setting (1.3 mg/kg per hour to 3.3 mg/kg per hour).
Long Term Prevention
In many studies, Lamotrigine has shown good results as first-line therapy for these disorders, with up to 80% of patients report improvement. With effective daily doses range from 100 mg to 400 mg. Carbamazepine and oxcarbazepine - effective in doses up to 900 mg/day. Topiramate and gabapentin (600 mg per day to 3600 mg per day) have also shown reported benefits.
1) Greater occipital nerve block has shown some benefits.
2) Peripheral nerve blocks, including infra and supraorbital nerve blocks, also have shown benefit in previous studies.
The lack of response to indomethacin and the response to intravenous lidocaine, are useful in diagnostic and therapeutic terms.
The natural history of SUNCT is not clear because of its clarity. However, patients with SUNCT and SUNA have been known to have their condition for up to 46 years. There is no correlation with mortality, and the disease is not fatal. Prognosis at present is improving, as more treatment strategies become available.
Syndrome itself does not have any long term neurological sequelae/complications. Most individuals present as normal between attacks. The social and economic burden of SUNCT is unknown.
There are no identified risk factors and, thus, no known prevention for SUNCT syndrome. In some patients, the background interictal pain in SUNCT may be attributable to migrainous biology and an analgesic overuse syndrome. Thus patients need to be educated about analgesic medication overuse. Overuse of medication can worsen this condition by increasing the frequency of attacks and severity.
The diagnosis of SUNCT and SUNA is vital as many differential diagnoses are very similar. History taking is an essential step in the evaluation of these patients. Also, proper workup to rule out all secondary causes of facial pain like vascular loop near the trigeminal nerve is essential. All members of the healthcare team should be familiar with this condition as it is not very common, but they do occur in the real world and must be well managed.
A multidisciplinary approach is necessary for the management of SUNCT, which includes the primary care physician (PCP), neurologist, nursing staff, and the pharmacy. A prompt referral is necessary from the PCP to a neurologist for early diagnosis and management of this condition because of its debilitating nature. This article summarizes vital features in recognizing this condition, whether it is in the emergency room, primary office visit, or on the neurology wards. Although it is not a very common condition, it could present as a very serious possibility if not adequately investigated; therefore, this educational activity could help many professions to understand and co-manage SUNCT/SUNA.
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