Sphenopalatine neuralgia as a differential diagnosis of complex regional pain syndrome of face

Abstract

We read with great interest the case report by Dr Hunter Collins, ‘Complex Regional Pain Syndrome Involving the Head and Face After Severe Malignant Otitis Media and Mastoiditis’. This case report is an opportunity to discuss sphenopalatine neuralgia, an entity first described in 1908 by Greenfield Sluder. Due to overlap in the clinical features such as head/face pain, vasomotor/sudomotor features and motor abnormalities associated with pain, and response to sphenopalatine ganglion block, sphenopalatine neuralgia is a close differential diagnosis of complex regional pain syndrome (CRPS) of face. Sphenopalatine neuralgia is associated with many treatable causes related to diseases of paranasal sinuses and nasal septum.

To the Editor,

We read with great interest the case report by Dr Hunter Collins, ‘Complex Regional Pain Syndrome Involving the Head and Face After Severe Malignant Otitis Media and Mastoiditis’. ¹ The patient presented with persistent left-sided face/head pain with discrete episodic swelling, localized autonomic symptoms, sudomotor and trophic changes following severe otitis media and mastoiditis. The involvement of sensory, vasomotor, sudomotor and trophic changes on the face fulfilled the Budapest diagnostic criteria for complex regional pain syndrome. The clinical features of the patient did not meet ICHD 3^rd edition criteria for migraine, trigeminal autonomic cephalalgia or any other primary or secondary headache.

This case report has given us an opportunity to discuss about sphenopalatine neuralgia, an entity first described in 1908 by Greenfield Sluder. Sphenopalatine ganglion or pterygopalatine ganglion is a major parasympathetic ganglion of the face that also provides a pathway for post-ganglionic sympathetic and sensory fibres to face. It serves secretomotor, autonomic, sensory and gustatory functions for face, eye, nasal and oral mucosa. ² Sluder described continuous/episodic pain with exacerbation that occurred in and around eye, root of nose, lower face, extending to mastoid and occipital region in his patients. Pain was associated with hypo/hyperesthesia in trigeminal distribution of the face including oral/palatal mucosa. Vasomotor/sudomotor features such as nasal congestion, swelling, rhinorrhoea, conjunctival injection, lacrimation, sweating and motor abnormalities such as elevated palatal arch on affected side, uvula shifted to opposite side and a dimple appearing on the raphe just above the uvula in the act of gagging were also reported.^3,4 After Sluder's original description, a number of case reports/series were published mostly by dental and oromaxilofacial specialists that described wide range of clinical features secondary to sphenopalatine neuralgia. A meta-analysis of case reports/case series published in 2019 analysed 81 previously published cases and also presented 10 new cases. As per the meta-analysis, sphenopalatine neuralgia involves head (temporal/frontal) and facial pain with pain attacks lasting few minutes to several days. In majority of patients, pain attack lasted from 180 min to 1 week. Total disease course was from one week to one year or more. The pain was triggered by emotional stress, exposure to cold, tooth damage and nasal surgery. ⁵ Considering the involvement of sensory/motor/autonomic/sudomotor systems, a patient with sphenopalatine neuralgia will also fulfil the Budapest criteria for complex regional pain syndrome (CRPS). In ICHD 3^rd edition, sphenopalatine neuralgia is described as a synonym of cluster headache. ⁶ However, there are striking differences from cluster headache such as long pain attacks lasting days, lack of circadian/circannual rhythmicity, lack of response to oxygen inhalation, large proportion of patients showing structural lesions in vicinity of sphenopalatine ganglion and response to removal/treatment of underlying nasal septal spur/deviation, sinusitis or other cause and improvement in pain by cocainization of sphenopalatine ganglion.^3,5 Though sphenopalatine block has been shown as effective in cluster headache by some authors, this has not been a regularly offered treatment for cluster headache. The entity of sphenopalatine neuralgia went into disrepute despite many case reports/series, meta-analysis and reviews favouring sphenopalatine neuralgia as an independent entity. The most probable reason for this entity to not find its due recognition and a place in the appendix of ICHD is a non-uniform clinical presentation described under the umbrella of sphenopalatine neuralgia by many authors.

The patient presented by Dr Collins had many similarities with sphenopalatine neuralgia such as left-sided temporal, frontal, orbital/periorbital and facial pain that was unremitting and had exacerbations. There were vasomotor and sudomotor changes on face associated with pain. The pain responded to sphenopalatine ganglion block. However, there were certain differences such as presence of ptosis, lack of nasal/eye vasomotor abnormalities such as conjunctival injection, lacrimation or rhinorrhoea and lack of hair on the affected side of face. Differences in temperature on either side of face can occur due to hypo or hyperhidrosis (sudomotor changes) as well as vasomotor changes that produce changes in skin colour and temperature. Since CRPS of face and sphenopalatine neuralgia have considerable overlap in clinical features and both show response to sphenopalatine ganglion block, we believe that sphenopalatine neuralgia should be considered as a differential diagnosis of CRPS. It is also important because unlike CRPS of face that does not have any underlying treatable cause, sphenopalatine fossa can be visualized on appropriate sections of computed tomography and magnetic resonance imaging and nearly 70% of patients with sphenopalatine neuralgia have an underlying cause related to sinus infection, nasal septum or nasal mucosa. ⁵ Dr Collin's patient had otitis media that precipitated CRPS. In nearly 15% patients, otitis media is caused Eustachian tube dysfunction secondary to sinusitis. ⁷ Therefore, it appears worthwhile to look for sinusitis in view of CRPS phenotype (resembling sphenopalatine neuralgia) occurring after otitis media in Dr Collin's patient.

We conclude that unilateral headache with facial pains, vasomotor/sudomotor features and motor abnormalities of face/palate can occur secondary to sphenopalatine neuralgia, and it should be considered a close differential diagnosis of CRPS of face.