the Value of Sensory Index in Trigeminal Neuralgia

Trigeminal neuralgia (TN) is defined by the International Headache Society (IHS) as "unilateral disorder characterized by brief electric shock-like pains, abrupt in onset and termination, and limited to the distribution of one or more divisions of the trigeminal nerve". It is considered the worst type of facial pain and described as intense, sharp, stabbing, and shooting like electric shock pain. It can be triggered by touch, chewing, laughing, shaving or face wash .

The IHS suggests a classification of TN as either classic (essential or idiopathic) TN (CTN) or symptomatic TN (STN; pain indistinguishable from that of CTN, but caused by a demonstrable structural lesion other than vascular compression).Treatment of TN is conservative, surgical or interventional. Pharmacotherapy with carbamazepine is tried early in cases of TN but has many side effects .Other medications can be used in the treatment of TN, include oxycarbazepine, gabapentin, pregabalin, baclofen, valproate, clonazepam, phenytoin, and lamotrigime .

The most clinically appropriate treatment includes surgical microvascular decompression (MVD), stereotactic radiation therapy, gamma knife (SGK), percutaneous balloon decompression, percutaneous glycerol rhizolysis, percutaneous radiofrequency (RF) of the Gasserian ganglion (GG), and GG stimulation and neuromodulation. Interventional therapies for TN are of variable efficacy and safety, and have different results for different periods of time before the recurrence of symptoms. Interventional therapy for TN is either destructive with trigeminal nerve sensory function destroyed intentionally or non-destructive with decompression of the trigeminalnerve and preservation of its regular function. The most common procedures in treating TN pain are the use of radiofrequency (RF) .

Radiofrequency thermos-coagulation of the GG is thought to selectively destroy the pain fibers by thermos-coagulation at > 65°C , that helps reduce pain and prevent triggering, but can cause bothersome dysesthesia. Another method, pulsed radiofrequency (PRF) which defined as the delivery of short pulses of RF via a needle tip, thereby a short exposure at the same temperature will result in less thermal tissue destruction (6).

Combined conventional and pulsed radiofrequency (CCPRF) achieved comparable pain relief to PRF treatment alone in patients with chronic pain, the combination of PRF and CRF would increase the effect of CRF and reduce the need for long-duration CRF (LCRF) and its attendant side effects .

The main objective of this study is to assess the possible value of motor index as a prediction of success of radiofrequency lesioning of the Gasserian ganglion during treatment of trigeminal neuralgia.

Inclusion criteria

• Patients with trigeminal neuralgia, diagnosed in accordance with the International Headache Society (7) and with a visual analogue score (VAS) for pain of at least 7 or more for a minimum of 3 months before the intervention .
• Patients on a stable analgesic regimen for 2 weeks (consisting of at least two analgesics, including anticonvulsants) before the intervention .
• Patients examined by use of MRI/A of the brain to exclude secondary neuralgia.

Exclusion criteria

• Patients with severe mental or psychiatric disorders
• Patients with history of drug abuse, high intracranial tension and history of MVD, SGK, balloon compression, RF treatment, or glycerol injection
• The possibility of vascular loop compression and other causes of TN