TRIGEMINAL NEURALGIA

Natural History and Treatment Options

 

Background

Trigeminal neuralgia (TN), also known as tic douloreux, is a chronic debilitating and painful condition affecting the face. It is characterised by a sudden, severe, electric shock-like or stabbing pain typically felt on one side of the jaw or cheek (in the trigeminal nerve distribution). The pain would last from a few seconds to minutes per each episode, followed by a refractory (pain-free) period. The pain may be triggered by light mechanical touch to the face (trigger point or trigger zone). The attacks are sporadic and may occur at intervals, many times a day or, in rare instances, follow one another almost continuously. Periodicity is characteristic, with episodes occurring for a few weeks to a month or two, followed by a pain-free interval of months or years and then recurrence of another bout of pain.

 

Trigeminal neuralgia affects women more commonly, and typically involves the cheek (maxillary division of the Trigeminal nerve, V2) more than the jaw (mandibular division of the Trigeminal nerve, V3) and less commonly the forehead (Ophthalmic division of the Trigeminal nerve, V1). The most common cause of TN is a compressing loop of an artery (typically the superior cerebellar artery). However, other vascular abnormalities such as a dolichoectatic vertebrobasilar complex, persistent fetal trigeminal artery, an aberrant loop of the anterior inferior cerebellar artery (AICA) or a tumour can be the cause.

 

Natural History

Most cases of TN are misdiagnosed initially, and the correct diagnosis is delayed for weeks to years. Typically, patients present for medical attention following multiple dental check-ups and procedures to no avail. Attacks of pain present for weeks to months with periods of remission lasting for months to years.  Almost invariably the pain recurs with increasing duration, frequency, and severity – mandating re-evaluation of the initial diagnosis (if that of TN was not made).

The initial response to treatment with Carbamazepine (Tegretol) is generally excellent. Around 80% of patients experienced symptomatic relief following commencement of Tegretol. This initial positive response drops to 66% over time. Even patients that have an unsatisfactory response to Carbamazepine, would often have an initial partial response within the first 48 hours. However, around one in four patients stop taking Tegretol due to ongoing pain or significant side effects, requiring a reduction in the dosage or changing medications.

Treatment Options

Optimal management for TN should include a multidisciplinary approach involving the neurologist, neurosurgeon, and pain management physician.  Conservative management with medical therapy should be initially attempted in all patients.  If this fails, the main treatment options are surgery for microvascular decompression (MVD), percutaneous ablative procedures (balloon micro compression, radiofrequency thermocoagulation, and glycerol injection) and stereotactic radiosurgery (SRS).

 

Microvascular Decompression

Microvascular decompression (MVD) of the trigeminal nerve is the treatment of choice. MVD is generally recommended for patients with inadequate medical control. Patients who benefit most from this type of surgery are:

  • those with disease duration for less than 5 years,

  • there is proven arterial compression of the Trigeminal nerve on MRI scan, and

  • those who has classic “Type 1” facial pain.

 

Based on available literature, at least 85% (range 67 to 100%) of patients experienced resolution of pain and remain off medications following MVD surgery.  When patients were reported as being pain-free but still taking medication following MVD surgery, the success rate improved to 95% (range 70.3-100).  The benefit of surgery is also long lasting, with more than 80% of the patients remaining pain-free at 7 years. Recurrence of pain following MVD is reported to be between 6 to 30%.

 

Percutaneous Ablative Procedures.

The three percutaneous ablative procedures (radiofrequency thermocoagulation, balloon compression, and glycerol/alcohol injection) are used for patients who are a poor anaesthetic risk, the elderly, patients with MS, and patients who decline a microvascular decompression.

Percutaneous radiofrequency thermocoagulation

  • Initial success rate = 91-100%

  • Failure rate = 3 to 6%

  • Failure over time = 50%

  • Recurrence = 20%

Glycerol/Alcohol Injection

  • Initial success rate = 73-97%

  • Failure rate = 5-20%

  • Failure over time = 40%

  • Recurrence = 18%

Balloon Compression

  • Initial success rate = 60-98%

  • Failure rate = 10%

  • Failure over time = 30-100%

  • Recurrence = 5-77%

Stereotactic radiosurgery (SRS)

The role and usefulness of stereotactic radiosurgery (SRS) is emerging. It is the least invasive and ideal for patients who are deemed too high risks for surgery.  In some series, the results are comparable to those of MVD surgeries. Initial success rate of SRS is around 90%, but this can drop to 32% over time. After SRS, there is a delay to treatment effect of weeks to months, and some patients may need to wait 12 months to be pain-free.  The recurrence rate ranged from 19 to 44%.

 

Patients who are ideal for SRS are those who:

  • Can tolerate a higher radiation dose (i.e., more than 70 Gy)

  • Have not had prior MVD surgery

  • Have typical “Type I” facial pain

 

 

Some useful references

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