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Neuropathic Pain
Advances in Trigeminal Neuralgia
a report by
Giorgio Cruccu
Secretary General, European Federation of Neurological Societies, and
Professor of Neurology, Department of Neurological Sciences, La Sapienza University, Rome
Recently, certain aspects of trigeminal neuralgia (TN) and its history alone. Pain distribution is unilateral (bilateral TN sometimes occurs
management have been clarified. After a reminder of the general in multiple sclerosis) and follows the sensory distribution of the trigeminal
concepts of TN, this article describes these recent developments with divisions, typically radiating to the maxillary (V2) or mandibular (V3)
regard to new views about the criteria for diagnosing symptomatic territories. Ophthalmic (V1) pain is less common and was previously
forms, clarification about medical treatment and a proposal about the considered indicative of symptomatic TN (see below).
choice of surgical procedures.
Strongly indicative of a symptomatic form, a focal neuropathy is often a
TN, or ‘tic douloureux’, is most easily recognised in medical practice as pain in the tongue, which is very rarely affected in classic TN. The pain
“a sudden, usually unilateral, brief stabbing recurrent pain in the is never felt in the teeth.
10
The right side of the face is involved more
distribution of one or more branches of the fifth cranial nerve”.
1
TN may frequently than the left, and the disorder is more common in women
have no apparent cause (idiopathic, essential or classic TN) or be than in men (3:2). Pain, usually referred to as stabbing or electric-shock-
secondary to major neurological disease (symptomatic TN). Symptomatic like, is brief and paroxysmal, lasting a few seconds, with no pain between
TN can be related to slowly growing tumours, such as cholesteatomas, paroxysms. However, there is sometimes an after-pain described as
meningiomas or neurinomas of the VIII nerve that compress the slowly fading away. Pain may be provoked by stimulating cutaneous or
trigeminal nerve root near the dorsal root entry zone, or multiple mucous trigeminal territories (trigger zones). Gently touching the face,
sclerosis (MS), which is typically associated with TN.
2–4
Many washing, shaving, talking, brushing the teeth, chewing, swallowing or
investigators refute the term ‘idiopathic TN’ because they support the even a slight breeze can trigger the paroxysms. Pain provokes brief
view that, when no lesion affecting the trigeminal system can be muscle spasms of the facial muscles, thus producing the ‘tic’. Especially
demonstrated, TN is due to a vascular compression of the trigeminal in the early years of the condition, there can be long pain-free periods;
nerve root by tortuous or aberrant vessels. Microsurgical interventions in however, these remission periods gradually become shorter and shorter.
the posterior fossa always find a compressing vessel, most often the Classic TN occurs more often in the sixth or seventh decade of life and is
superior cerebellar artery. Further support for this view comes from stereotyped in each individual.
magnetic resonance imaging (MRI) studies reporting a frequent contact
between vessels and the trigeminal root.
5
Microvascular decompression Differential Diagnosis Between Classic and
consistently relieves TN pain.
6
Nevertheless, other investigators do not Symptomatic Forms
support the view that a vascular compression is the main factor, as About 15% of cases are secondary to major neurological disease such as
compression of the trigeminal nerve root near the root entry zone is tumours or MS.
7
How does one identify these patients? Traditionally, the
often found (in 7–12% of cases) during standard autopsy of patients clinical features that were considered indicators of probable symptomatic
with no history of TN, and on MRI TN patients may have bilateral TN were bilateral pain, finding of sensory deficits, involvement of the
compressions but no bilateral symptoms.
7,8
Several factors possibly ophthalmic division, unresponsiveness to medical treatment and onset
contribute to the development of TN. The hypothesis of a multifactorial age below 50 years.
origin is favoured by several investigators.
In a recent systematic review of the evidence-based literature, a joint
As the debate about the possible causes of idiopathic TN is still open, we European–American task force arrived at conclusions that differ from the
believe that the terminology and definitions proposed by the above notion in several respects.
7
Bilateral pain has a 100% specificity,
International Headache Society (IHS)
9
are the most appropriate. Classic but its occurrence is too rare even in symptomatic TN (sensitivity 0–7%).
TN has no apparent cause other than vascular compressions, and The finding of sensory deficits is highly specific (98%), but the sensitivity
symptomatic TN is pain indistinguishable from that of classic TN but is is only 37%. In other words, the finding of sensory deficits or bilateral
caused by a demonstrable structural lesion other than vascular pain is an excellent indicator of symptomatic TN, but their absence does
compressions.
9
The categorisation of TN into typical and atypical forms is not indicate classic TN. The involvement of the ophthalmic division is
based on symptom constellation and not aetiology, thus typical TN must equally rare in the two forms (21 and 23%, respectively). Similarly, there
not be confused with classic TN.
7
was no significant difference in response to treatment. The mean onset
age was significantly lower in symptomatic (48 years) than in classic TN
Although trigeminal neuralgia is classified as neuropathic pain because it (57 years), but a histogram of onset age distribution showed that there
is a direct consequence of somatosensory system lesion, it has unique was considerable overlap in the age ranges of the two populations. Thus,
features that make it different from other neuropathic pain. TN although younger age increases the risk of finding symptomatic TN, the
symptoms are unmistakable, and TN is usually recognisable by patient diagnostic accuracy of age as a predictor of symptomatic TN is too low to
© TOUCH BRIEFINGS 2007 35
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