Trigeminal neuralgia
Trigeminal neuralgia - Classification:
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Trigeminal neuralgia
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Type 1 (episodic)
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Type 2 (constant)
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Trigeminal neuropathic pain
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Trigeminal deafferentation pain
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Post-shingles trigeminal neuralgia
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Multiple sclerosis trigeminal neuralgia
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Atypical facial pain
Trigeminal neuralgia - Differential diagnosis:
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Idiopathic (95% of cases)
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Pontocerebellar angle tumor
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Squamous cell tumor
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Meningioma
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VIII neuroma
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Multiple sclerosis
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Posttraumatic
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Post-herbal
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Post surgery
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Post-radiotherapy, etc ...
Idiopathic trigeminal neuralgia - Treatment options:
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Drugs (Trileptal, ...)
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Gasser's ganglion thermocoagulation (RF lesion)
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Gasser's ganglion cistern balloon
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Glycerolization of the Gasser's ganglion
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Radiosurgery (Range-Knife, ...)
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Microvascular decompression
Trigeminal Neuralgia: Surgical Options
Surgical options will generally be considered in the event of drug treatment failure. However, there are cases when the drugs provide good relief to the patient, but produce too many side effects. In these situations, it is then legitimate to also consider surgery.
Surgical options:
The surgical choices will be similar for trigeminal neuralgia linked to lesional involvement such as multiple sclerosis.
In the case of idiopathic neuralgia, the model of microvascular compression opens up the more "etiological" alternative of decompression.
Rhizotomies:
By rhizotomies is meant a voluntary lesion of the trigeminal roots (between the brainstem and the Gasser's ganglion). A somatotopy of these roots is present, which makes it possible to qualify the effect on the 3 trigeminal branches.
When we talk about thermocoagulation (RF lesion) of the Gasser's ganglion, it is in fact mainly rhizotomies.
Trigeminal neuralgia: Gasser ganglion thermocoagulation (RF)
Gasser's ganglion thermocoagulation:
By means of a cannula inserted through the foramen ovale, it is possible to achieve targeted lesions of the roots leading to the Gasser's ganglion.
Somatotopic identification is done using 3 elements:
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The position of the needle in relation to the line of the clivus in lateral fluoroscopy
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Stimulation that causes paresthesias in the dermatome corresponding to one of the 3 trigeminal branches
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Vasodilation of the corresponding dermatome
Once the target is determined, the same electrode is used to heat the area (radiofrequency lesion). Loss of sensitivity (hypoesthesia) results.
Radiofrequency generating devices used for thermocoagulations of the Gasser ganglion. The device on the left is manufactured by Elekta and the device on the right by Radionics.
Ablative procedures - Risks and side effects:
Thermocoagulation is the prototype of the ablative procedure, but balloon, glycerol, radiosurgery or open rhizotomy techniques are also part of it and have essentially the same flaws:
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Loss of feeling . There is a link between loss of sensitivity and the duration of the effect. For this reason, these techniques are often performed with restraint the first time around so that the patient understands the significance of this loss of sensitivity. For the 3rd branch of the trigeminal (mandibular branch), this has relatively little impact. The 2nd branch (maxillary branch) has more potential impact because the lower part of the cornea is innervated by this branch. As a general rule, the corneal reflex (which has an essential role in protecting the cornea) is however preserved in the event of a partial lesion of this 2nd branch. The 1st branch (corneal branch) poses many problems because most of the cornea is innervated by this branch and the risk of causing the corneal reflex to disappear is high in the event of "too" aggressive treatment.
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Anesthesia dolorosa : If the sensory loss is major (regardless of the branch involved), the brain may interpret this loss of sensitivity as pain. This is the same mechanism as that for phantom pain that we encounter for example after an amputation.
Trigeminal neuralgia: Microvascular decompression
Microvascular decompression:
Even though the actual mechanism is more complicated than simple mechanical compression, vascular compression at the emergence of the trigeminal roots (brainstem) appears to play a major role in "idiopathic" trigeminal neuralgia.
The origin of the compression is often
combined (artery and vein) as the
summarizes the table opposite.
The operation is performed by a small retromastoid craniotomy.
Through this approach, good access to the emergence of the trigeminal brain stem is obtained and the origin of the compression can be identified.
If no convincing compression is found, it is possible to do a partial rhizotomy of the trigeminal roots under visual control.
This view through the operating microscope illustrates well the compression of the emergence of the trigeminal nerve by a loop of the superior cerebellar artery.
