Glossaries

Balloon compression A percutaneous (requiring a needle inserted through the skin of the cheek) neurosurgical procedure carried out at the Gasserian ganglion and/or pre-ganglionic nerve route. The procedure involves using a balloon to press the nerve against bony tissue which causes mechanical nerve destruction (partial nerve damage), and is designed to stop the transmission of pain signals to the brain by selectively damaging the small unmyelinated and small myelinated pain fibres of the trigeminal nerve while ideally sparing the rest of the nerve fibres. This minimally invasive procedure is also known as microcompression.

CyberKnife® radiosurgery A non-invasive stereotactic radiosurgery procedure that utlises a robotic arm technology that directs individual doses of radiation onto multiple points on the trigeminal nerve root. The procedure is usually performed with CT scan guidance, without the use of a stereotactic reference frame.

Gamma Knife® radiosurgery A minimally invasive stereotactic radiosurgery procedure that utilises a technology that focuses beams of radiation onto a very small spot (isocenter) within the trigeminal nerve root. The procedure is performed with a stereotactic reference frame that is temporarily attached to the head of the person undergoing the procedure, therefore, local anaesthesia is required. The dominant number of studies and volume of clinical outcomes data for stereotactic radiosurgery for trigeminal neuralgia utilises this technique.

Gasserian ganglion Cluster of nerve cells in which the three main branches of the trigeminal nerve meet. Also known as trigeminal ganglion or semilunar ganglion.

Glycerol rhizolysis A percutaneous (requiring a needle inserted through the skin of the cheek) neurosurgical procedure that involves using a viscous alcohol called glycerol to damage the Gasserian ganglion and/or pre-ganglionic nerve route. The procedure stops the transmission of pain signals to the brain by causing selective chemical damage to the small unmyelinated and small myelinated pain fibres of the trigeminal nerve while ideally sparing the rest of the nerve fibres. This minimally invasive procedure is also known as percutaneous retrogasserian glycerol rhizolysis.

LINAC-MLC-based radiosurgery Non-invasive stereotactic radiosurgery procedures that utilises technologies that focus small high-dose radiation beams onto specific points (focus spot) within the trigeminal nerve root (isocentric treatment). The technologies use a large high-energy linear accelerator (LINAC) x-ray source and have multileaf collimator (MLC) capability. Machines that utilise this technology include Novalis®, Trilogy®, and Truebeam®. The procedures are usually performed with CT scan guidance, without the use of a stereotactic reference frame.

Microvascular decompression A neurosurgical (microsurgical) procedure that involves accessing via the posterior fossa the trigeminal nerve just at its point of entry into the brain. Any vessels distorting or in close contact with the nerve are moved out of the way with the aim of avoiding nerve damage and hence preserving function. This procedure requires general anaesthetic. It is the only neurosurgical procedure designed to spare the trigeminal nerve from damage, and to directly address the cause of trigeminal neuralgia in most cases, rather than just relieve the symptom of pain. Results of this procedure vary the most from surgeon to surgeon.

Moderate-quality evidence Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.

Non-percutaneous destructive neurosurgical techniques Neurosurgical procedures that cause destruction (ablation) of specific nerves, but do not require needle insertion through the skin of the cheek (e.g., stereotactic radiosurgery [performed with technologies such as the Gamma Knife®]). Also known as non-percutaneous ablative surgical procedures.

Percutaneous destructive neurosurgical techniques Neurosurgical procedures that require needle insertion through the skin of the cheek, and that cause partial destruction (ablation) of the trigeminal nerve by selectively targeting damage to the small unmyelinated and small myelinated pain fibres of the trigeminal nerve, while ideally sparing the rest of the nerve fibres (e.g., radiofrequency thermocoagulation, glycerol rhizolysis, and balloon compression). Also known as percutaneous ablative surgical procedures.

Radiofrequency thermocoagulation A percutaneous (requiring a needle inserted through the skin of the cheek) neurosurgical procedure that uses an electrode to damage the Gasserian ganglion and/or pre-ganglionic nerve route. The procedure stops the transmission of pain signals to the brain by selectively damaging the small unmyelinated and small myelinated pain fibres of the trigeminal nerve while ideally sparing the rest of the nerve fibres. This minimally invasive procedure is also known as percutaneous retrogasserian radiofrequency thermocoagulation.

Stereotactic radiosurgery A non-percutaneous (does not require needle insertion through the skin of the cheek) neurosurgical procedure that involves using a focused beam of ionising radiation to selectively damage the small unmyelinated and small myelinated pain fibres of the trigeminal nerve, while ideally sparing the rest of the nerve fibres. While several technologies purport similar results (CyberKnife® radiosurgery and other LINAC-MLC-based radiosurgery technologies), the predominant and proven technology for this non-invasive neurosurgical technique is the Gamma Knife®.

Very low-quality evidence Any estimate of effect is very uncertain.