Excerpt from Trigeminal Neuralgia

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Background

Trigeminal neuralgia (TN) is a common and potentially disabling pain syndrome, the precise pathophysiology of which remains obscure. Although neurologic examination findings are normal in patients with the idiopathic variety, the clinical history is distinctive. The initial response to carbamazepine therapy typically is diagnostic and successful. Despite obtaining this satisfying early relief with medication, patients may experience breakthrough pain that requires additional drugs and, in some patients, one or more of a variety of surgical interventions.

Historical note

In 1900, in a landmark article, Cushing reported a method of total ablation of the gasserian ganglion to treat TN.

In 1912 Osler described TN as follows:

• In patients with advanced TN, the paroxysms follow one another rapidly without any assignable cause, and in the intervals the patient may never be quite free from pain.
• They are initiated by almost any form of external stimulus, for example by a draught of air; movement of the facial muscles or tongue while speaking; touching the skin, particularly over those points from which the pain seems to take its origin; and the act of swallowing, especially when the pain involves the mucous membrane field of distribution of the nerve.
• It is not a self-limited disease. In some instances, the neuralgia reaches such a frightful intensity that it renders the patient's life unbearable. In earlier times, suicide was not an uncommon consequence.

Pathophysiology

Usually no structural lesion is present, although many investigators agree that vascular compression, typically venous or arterial loops at the trigeminal nerve entry into the pons, is critical to the pathogenesis of the idiopathic variety. This compression results in focal trigeminal nerve demyelination.

Since the exact pathophysiology remains controversial, TN may have either a central and/or peripheral etiology.

Frequency

United States

According to Penman in 1968, the prevalence of TN is approximately 107 men and 200 women per 1 million people. Mauskop states that approximately 40,000 patients in the US suffer from this condition at any particular time. The incidence is 4-5 cases per 100,000.

Rushton and Olafson found that approximately 1% of patients with multiple sclerosis (MS) develop TN, whereas Jensen et al stated that 2% of patients with TN have MS.

Mortality/Morbidity

• TN is not associated with a shortened life. However, the morbidity associated with the chronic and recurrent facial pain can be considerable if the condition is not controlled adequately.
• Individuals may choose to limit activities that precipitate pain, such as chewing, possibly losing weight in extreme circumstances.
• TN may evolve into a chronic pain syndrome, and patients may suffer from depression and related loss of daily functioning.

Race

No racial risk factors have been identified.

Sex

The male-to-female ratio is 2:3.

Age

• Age of onset typically is 60-70 years; thus, advanced age is a major risk factor.
• Patients who present with the disease when aged 20-40 years are more likely to suffer from a demyelinating lesion in the pons secondary to MS.
• MS and hypertension are the 2 risk factors found in epidemiologic studies.

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