*Migraine *Dental diseases *Neoplasia *Infection<unk>  and AO can be difficult to diagnose, and are often misdiagnosed with resultant inappropriate attempts of treatment, e.g. root canal therapy which may at best have only a temporary benefit, or at worst lead to an increase in the<unk> . Excluding an organic cause for the<unk>  is the most important part of the diagnosis. Odontogenic<unk>  should especially be ruled out, since this accounts for over 95% of cases of orofacial<unk> . There is considerable symptom overlap between<unk>  and temporomandibular joint dysfunction. The diagnosis of<unk> <unk>  generally is often multidisciplinary. Classification<unk>  has also been described as a medically unexplained symptom, which are thought by some to be largely psychogenic in nature. However, true psychogenic<unk>  is considered to be rare. Some sources have assigned or categorized<unk>  as a psychosomatic manifestation of somatoform disorder, as defined in the Diagnostic and Statistical Manual of the American Psychiatric Association. Distinction should be made between somatoform disorder, where affected individuals are not inventing the symptom for some benefit, and other conditions like factitious disorder or malingering. Recent evidence in chronic<unk> <unk>  research appear to suggest that a proportion of individuals who have been diagnosed with<unk>  have neuropathic<unk> ,<unk>  is described as one of the 4 recognizable symptom complexes of chronic<unk> <unk> , along with burning mouth syndrome, temporomandibular joint dysfunction (TMD) and<unk>  odontalgia. However, there is a degree of overlap between the features of these diagnoses, e.g. between<unk>  and TMD and burning mouth syndrome.<unk>  odontalgia is similar in nature to<unk> , but the latter term generally is used where the<unk>  is confined to the teeth or gums, and<unk>  when the<unk>  involves other parts of the face. Other sources use<unk>  odontalgia and<unk>  as synonyms, or describe<unk>  odontalgia as a sub-type, variant, or intra-oral equivalent of<unk> . Sometimes "phantom tooth<unk> " is listed as a synonym for AO, and sometimes it is defined as toothache which persists after a tooth has been extracted. It has been suggested that it is likely that these terms do not represent a single, discrete condition, but rather a collection of misdiagnosed and as yet unidentified causes. This<unk>  is often similar to<unk>  from organic dental disease such as periapical periodontitis, or pulpitis (toothache), but unlike normal dental<unk> , it is not relieved in the long term by dental treatments such as endodontic therapy (root canal treatment) or tooth extraction, and it may even be worsened, return soon after, or simply migrate to other areas in the mouth following dental treatment. Definitions<unk>  There is no universally accepted definition of<unk> , and it is defined less by what it is as what it is not. Various definitions of<unk>  include: * "a nonmuscular or joint<unk>  that has no detectable neurologic cause." * "a condition characterized by the absence of other diagnoses and causing continuous, variable-intensity, migrating, nagging, deep, and diffuse<unk> ." * "a continuous unilateral deep aching<unk>  sometimes with a burning component." *<unk> <unk>  not fulfilling other criteria" (previous IHS definition, which now uses the term "Persistent idiopathic<unk> <unk> ", see below). * "persistent<unk>  in the maxillofacial region that does not fit the diagnostic criteria of any other orofacial<unk>  and has no identifiable cause." (Neville et al.)<unk>  odontalgia There are no globally accepted definitions of AO, but some suggested definitions are listed below: * "continuous<unk>  in the teeth or in a tooth socket after extraction in the absence of any identifiable dental cause," (International headache society, description included as a side note of "persistent idiopathic<unk> <unk> " in the ICHD-2, i.e. with is no separate diagnosis for<unk>  odontalgia). * "Severe throbbing<unk>  in the tooth without major pathology" (IASP definition in the "Classification of Chronic<unk> ", listing AO as "tooth<unk>  not associated with lesions"). * "pain and hypersensitive teeth in the absence of detectable pathology". * "pain of an unidentifiable cause that is perceived to be originating in a tooth or teeth". Naming controversy and proposed replacement terms The term<unk> " has been criticized. Originally,<unk>  was intended to describe a group of individuals whose response to neurosurgical procedures was not<unk> . Some experts in<unk> <unk>  have suggested that the term<unk>  be discarded, as it may serve as a catchall phrase to describe either individuals who have not had an adequate diagnostic assessment or individuals whose<unk>  is purely psychogenic.<unk>  has also been described as an inappropriate term since many cases in this category conform to a recognizable pattern. Another cited reason for discontinuing use of the term<unk>  is that some cases appear to follow surgeries or injuries involving the face, teeth and gums, possibly suggesting infectious or traumatic etiologies. Some classifications of<unk> <unk>  avoid the term in favor of other similar terms. The IHS now use the term "Persistent idiopathic<unk> <unk> " in the ICHD-2, defining it as "persistent<unk> <unk>  that does not have the characteristics of the cranial neuralgias ... and is not attributed to another disorder." The IASP's Classification of Chronic<unk>  does not have a diagnosis that corresponds to<unk> , although it is listed in the differential diagnosis of "Glossodynia and sore mouth" (Burning mouth syndrome). However, in another IASP publication from 2011, the term PIFP is used and defined almost identically to the above. Despite the controversy surrounding the use of the term, it has a long history, and it is still in common use by clinicians to refer to chronic<unk> <unk>  that does not meet any diagnostic criteria and does not respond to most treatments. Re-classification of trigeminal neuralgia + Classification scheme for trigeminal neuralgia (TN) and related<unk> <unk>  syndromes. Type Description TN1 Classic or<unk>  TN. Idiopathic, spontaneous<unk> <unk>  which is predominantly episodic in nature TN2<unk>  TN, or TN type 2. Idiopathic, spontaneous<unk> <unk>  which is predominantly constant in nature TN3 Trigeminal neuropathic<unk> . Results from unintentional injury to the trigeminal nerve from trauma or surgery. TN4 Trigeminal deafferentation<unk> . Results from intentional injury to the nerve in an attempt to treat either TN or other related<unk> <unk> . TN5 Symptomatic TN. Results from multiple sclerosis TN6 Postherpetic TN. Follows a cutaneous herpes zoster outbreak in the trigeminal distribution. TN7<unk> ."<unk> <unk>  secondary to a somatoform<unk>  disorder, requiring psychological testing to confirm. Trigeminal neuralgia is another example of a cause of<unk> <unk> . Neuralgia refers to<unk>  in the distribution of a nerve (or nerves), and commonly implies paroxysmal (sudden)<unk> , although the accepted IASP definition specifies that the term should not be restricted to mean paroxysmal<unk> . Classic trigeminal neuralgia refers to sudden, shooting<unk>  in the face, which is usually short lived and brought on by accidental stimulation of trigger points on the face, as may occur when washing. Trigeminal neuralgia has been described as one of the most<unk> ful conditions possible. Trigeminal neuralgia and<unk>  are traditionally considered separate, since<unk><unk> ly involves constant, often burning<unk>  and trigeminal neuralgia classically shows paroxysmal, shooting<unk> , but in reality there is some overlap in their features. In 2005 researchers proposed a new classification of trigeminal neuralgia which described a type of trigeminal neuralgia where the<unk>  was constant and burning. They theorized that this type was a progression of untreated classic trigeminal neuralgia, and represented worsening neural injury. There were seven proposed sub-types of trigeminal neuralgia (TN) in this classification (see table), and the final category was reserved for<unk> <unk>  caused by somatoform disorder. This last category (TN7) was termed<unk> , although many cases that would otherwise be traditionally labelled as<unk>  would fall into other groups in this classification, especially into the second group. In a publication of the Trigeminal Neuralgia Association (TNA), the following was said about this new classification and<unk> : "The term<unk><unk>  neuralgia or<unk>  was a wastebasket term applied by a serious contributor of a former era to a group of patients he did not understand. Many of these patients were our trigeminal neuralgia type 2 patients. It is unfortunate that many of these people were told they had psychological problems. Many developed psychological problems after the fact when told by everyone that such was their problem. Over the years, our areas of ignorance have progressively narrowed. ... A non-pejorative and, hopefully, reasonable term for the ever-narrowing group of undiagnosed face<unk>  problems: Facepain of Obscure Etiology (FOE or POE) to replace<unk>  in the Burchiel classification." As a result, some sources list terms such as<unk>  trigeminal neuralgia", "trigeminal neuropathic<unk> " and<unk><unk>  neuralgia" as synonyms of<unk> . ICHD-2 Diagnostic criteria The ICHD-2 lists diagnostic criteria for "persistent idiopathic<unk> <unk> " (the term that replaces<unk>  in this classification): ::A.<unk>  in the face, present daily and persisting for all or most of the day, fulfilling criteria B and C, ::B.<unk>  is confined
Atypical facial pain
Nablus mask-like facial syndrome
Necrospermia
Symmastia
Dogger Bank itch
Pellagra
Trypophobia
Focal hyperhidrosis