Abstract
The objective was to formulate distinctive criteria to substantiate our opinion that Sluder's neuralgia and cluster headache are two different clinical entities. A systematic review was carried out of all available, original literature on Sluder's neuralgia. Pain characteristics, periodicity and associated signs and symptoms were studied and listed according to frequency of appearance. Eleven articles on Sluder's neuralgia were evaluated. Several differences between Sluder's neuralgia and cluster headache became evident. Based on described symptoms, new criteria for Sluder's neuralgia could be formulated. Sluder's neuralgia and cluster headache could possibly be regarded as two different headache syndromes, and Sluder's neuralgia could be a trigeminal autonomic cephalalgia.
Introduction
Sluder's neuralgia
Sluder's neuralgia (SN) of the pterygopalatine ganglion (PPG) is, although rare, a disorder well known to otolaryngologists. The clinical picture first described by Sluder in 1908 is characterised by mostly unilateral, moderately severe, burning, boring or nagging headache, starting around the eye and the root or lateral side of the nose, radiating to the maxillary region and associated teeth, zygoma, mastoidal area and occiput, or even as far as the shoulder and arm. Pain can be either episodic, with attacks lasting hours to days, or continuous. Typically, the pain is accompanied by autonomic, motor or sensory signs ipsilaterally. Information on the incidence of SN is scarce, but the disorder is commonly described as rare.
Several causes for SN have been suggested, such as infection of the posterior ethmoid and sphenoidal sinus (Sluder's own theory) (1,2), trauma (in which case we would prefer to speak of Sluder's neuropathia) (3,4) demyelinisation (4) or the presence of intranasal contact points such as a spine of the septum impacting on the middle turbinate (5–7).
SN is classified as being synonymous with Vidian neuralgia by Bruyn (5) and Vail (8,9). The latter states that the referred pain in SN could be explained by activation of sympathetic nerve fibres.
Most of these theories are based on the hypothesis that the typical clinical picture of SN is produced by irritation of the PPG (1–3). The majority of these aetiologic factors for SN are diseases seen by otolaryngologists, who should be well acquainted with the clinical picture of SN.
However, many official headache classifications do not mention SN at all. In the first edition of the International Headache Society (IHS) classification, SN is mentioned among ‘previously used terms’ that also refer to CH. In the second edition, SN is not mentioned.
Sjaastad describes the clinical picture of SN, but considers Sluder's original description to be rather vague (10).
Cluster headache
Cluster headache (CH) (ICHD-II 3.1) is defined as attacks of very severe, strictly unilateral pain in the retro- or supraorbital region and/or the temporal region, lasting 15–180 min and occurring at a frequency ranging from once every other day to eight times per day. Pain is associated with one or more of the following: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, eyelid oedema, forehead and facial sweating, miosis and/or ptosis. Attacks occur in clusters lasting for weeks or months, separated by remission periods lasting for months or years (11).
The prevalence of CH is estimated to be between one person per 500 and one per 1000 (12,13). The specific cause of CH remains unknown, but several mechanisms have been suggested to play a role in its aetiology. A dysfunction of the central nervous system activates the so-called trigeminovascular system (a system of neurons innervating the cerebral vessels whose cell bodies are located in the trigeminal ganglion), and primary defects in the hypothalamic grey matter, which are held responsible for the episodic pattern of clusters in which pain attacks occur (12,14–17). The activation of a trigeminal parasympathetic reflex explains the parasympathetic symptoms that are seen in CH. The efferent component of this reflex is thought to run through the PPG (14–18).
In contrast to patients with SN, who are diagnosed by otolaryngologists, patients with typical CH are mostly referred to neurologists.
Are SN and CH different clinical disorders?
It has been stated that the headache diagnosed by otolaryngologists as SN and the headache diagnosed by neurologists as CH, are in fact the same clinical entity (19).
Some of the symptoms and features of SN and CH show overlap. For instance, although one of the characteristic features of SN is that pain can be blocked by cocainisation or infiltration anaesthesia of the PPG, positive results of this method have also been reported in CH (20–22).
However, several crucial differences distinguish the two (19,23). One of the most striking differences lies in the severity of pain. Pain in CH is often described as excruciating, is in many cases accompanied by restlessness or agitation (11) and can even lead to suicidal behaviour in some patients (24–26), whereas pain in SN is often described as moderately severe (1,5,6,19,27). Pain in CH is localized as orbital, supraorbital and/or temporal, whereas pain in SN is localized at the root or lateral side of the nose and intra- or periorbitally, radiating to the maxilla, mastoidal or occipital area, and even to the neck, shoulder and arm.
Another difference lies in the periodicity of pain. Whereas the characteristic feature of CH is the fact that attacks come in cluster periods, the pain in SN can be either continuous with or without exacerbations or episodic with attacks. Furthermore, attacks in SN seem to last much longer (hour(s) to days) than those in CH (15–180 min). The difference between duration of pain in SN and CH is most clearly seen in the upper time limit of attacks, although it is clear that the general lower time limit of hours in SN shows some overlap with the upper time limit of 180 min in CH. The lower time limit of SN attacks varies in the literature between1 h (23) and a few minutes (4). Also, attack duration of as short as between 10 and 30 min, rarely exceeding 2 h, has been described (28). It is therefore difficult to present an exact duration range of SN attacks, as there seems to be no consensus on duration of pain.
Also, the typical CH patient is different from the SN patient. The former is usually male, with age of onset between 18 and 40; the latter is mostly female, with age of onset between 30 and 50. These differences support our hypothesis that CH and SN are two independent clinical disorders. Criteria for CH are clear and well defined.
We would like to propose new, strict and clear criteria for SN that are able to distinguish it from other forms of facial pain, and can thus be helpful in making a correct diagnosis.
We performed a systematic review to provide a quantitative assessment of symptoms described in literature on which these new SN criteria can be based.
In this article, the terms headache and facial pain are used synonymously.
Methods
Study retrieval and selection
A computerised literature search was performed in the Pubmed database with search terms ‘Facial neuralgia’, ‘Sluder's neuralgia’and ‘Sphenopalatine ganglion neuralgia’. Reference lists from identified publications were screened to retrieve additional articles. Medical handbooks were also searched for reports (5). Only articles published in English and German were retrieved.
Characteristics of SN according to newly defined criteria
Reason for a particular feature to become a SN characteristic was a presence in at least four of the 11 articles retrieved, or a presence in Sluder's original description.
Results
Clinical features of SN and CH
Validation of criteria
A majority of the identified articles on SN are based on patient descriptions.
The original description of SN by Sluder is based on observations drawn from experience with 214 cases (1,2). The author has never seen all manifestations in one case. A study by Puig et al. described eight patients being treated via intranasal phenolization of the PPG, and summarizes their presenting signs and symptoms (3). This summary is limited to pain localization and associated signs and symptoms, but in these categories, five patients fit our newly defined criteria for SN.
Pollock et al. described a case report of one patient who fits all of our criteria for SN. Akhtar Kamal studied 56 patients diagnosed with SN, without presenting details on their symptoms (6). However, 52 patients experienced pain relief upon administration of a local anaesthetic agent at the PPG, thereby meeting one of our criteria for SN. Ryan and Facer described the clinical picture of SN on the basis of a series of 20 patients from the Mayo Clinic, fitting all of our criteria for SN (23). Although their patients experienced mostly unilateral pain, occasionally the pain was bilateral. Salar et al. studied seven patients, who all experienced pain relief upon cocainisation or infiltration anaesthesia of the PPG, thereby meeting one of our criteria for SN (29).
Thus, in the 11 identified articles on SN, a total of 306 patients were described; 235 (77%) fit all current criteria for SN, five (2%) fit most criteria and 59 (19%) fit one of the criteria for SN, and for seven patients no details were provided. Of the five patients who fit most criteria for SN, three patients fit one or more criteria for CH (i.e. rhinorrhoea, epiphora and/or retro-orbital pain).
Discussion
Criteria for SN remain vague and uncertain and vary widely in the literature, which makes diagnosis difficult. There seems to be no such thing as a standard clinical picture for SN. A study by Ahamed and Jones (19) focuses on analysing the features of SN, and compares them with CH, classic migraine and Cluster-tic syndrome. Having done this, however, they conclude that at present, the ‘best fit’ for patients with SN symptoms is CH. They also conclude that the term Sluder should be discarded as there are serious flaws in its original description. Ryan and Facer (23) mention a number of differences between SN and CH, but also suggest that possibly SN is merely a variant of CH.
Our systematic review shows that there does seem to be a common clinical picture for SN according to the matching features in several of its descriptions.
In order to appreciate the results of this review, its limitations should be discussed. A limitation of this study is the fact that original literature on SN is scarce. Criteria for SN thus could only be based on characteristics noted in as few as 11 articles.
SN and CH are often regarded as being part of the same clinical entity. But although the PPG seems to play a crucial role in the aetiology of both these syndromes, the literature shows several crucial differences between the two. We suggest that SN and CH could be two different headache syndromes, and thus, that SN could be an independent clinical entity. However, just like CH, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing, SN could be a trigeminal autonomic cephalalgia (TAC). The TACs are characterized by short-lasting headache with autonomic features (30,31). CH is currently known as the TAC with the longest duration, but SN could possibly be a TAC with longer attack duration than CH.
Because SN is a rare but incapacitating pain syndrome, and no intervention has as yet proven effective in terms of permanent pain relief, it is our opinion that correct classification is highly important in order to study new treatment options.