Although the symptoms associated with trigeminal neuralgia have been well documented, the root cause of this disease initially eluded most surgeons. Although early remedies were haphazard because of a lack of understanding about the condition, near the 20th century both medical and procedural therapies were established for the treatment of trigeminal neuralgia. These treatments include a variety of medications, chemoneurolysis, radiofrequency lesioning, percutaneous ablative procedures, stereotactic radiosurgery, and open rhizotomy and microvascular decompression. This report recounts the history of trigeminal neuralgia, from its earliest descriptions to the historical evolution of nonsurgical and surgical therapies.
Key points
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Although the earliest descriptions of trigeminal neuralgia as a clinical entity date back as early as the 1600s, the term tic douloureux was coined nearly a century after in 1756, by Nicholas Andre.
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Ablative techniques included percutaneous ablation with radiofrequency lesioning, glycerol chemoneurolysis, balloon microcompression, and stereotactic radiosurgery.
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Although Dandy initially observed neurovascular compression during his operation of partial trigeminal neurectomy, it was Jannetta who introduced the operating microscope to confirm these findings culminating in the microvascular decompression procedure.
Introduction
A horrid affliction in its full fury, trigeminal neuralgia (TN), also known as tic douloureux , has been a major neurosurgical concern since neurosurgery first emerged as a distinct surgical specialty in the early 20th century. In its classic form, TN results in episodes of intense, lancinating facial pain followed by a period of relief. However, even during these periods of relief, patients often live in fear and anticipation of the next episode. The earliest descriptions of TN as a clinical entity date back to the 1600s provided by prominent physicians at the time including Drs Johannes Michael Fehr and Elias Schmidt, secretaries of the Imperial Leopoldina Academy of the Natural Sciences, and famous philosopher John Locke. However, the term tic douloureux was not coined until nearly a century after in 1756, by Nicholas Andre ( Fig. 1 , left) who believed that the condition stemmed from a nerve in distress and classified it as a convulsive disorder. He conceptualized the disease in terms of convulsions and used the term tic douloureux to imply contortions and grimaces accompanied by violent and unbearable pain. In 1773, an English physician, Dr. John Fothergill (see Fig. 1 , right) presented his experience with 14 patient encounters and deemed the cause to be related to cancer rather than a convulsive disorder, thus coining the term, Fothergill’s disease . In his remarkable and accurate description, he stated, “The affection seems to be peculiar to persons advancing in years, and to women more than to men…The pain comes suddenly and is excruciating; it lasts but a short time, perhaps a quarter or half a minute, and then goes off; it returns at irregular intervals, sometimes in half an hour, sometimes there are two or three repetitions in a few minutes…Eating will bring it on some persons. Talking, or the least motion of the muscles of the face affects others; the gentlest touch of a handkerchief will sometimes bring on the pain, whilst a strong pressure on the part has no effect.”
Although the clinical description of this condition had been clarified by the end of the 18th century, it was not until the 1820s that Charles Bell localized this pain syndrome to the trigeminal nerve; thus, the condition was ultimately referred to as trigeminal neuralgia . Although the cause of TN remained elusive for a long time, a common denominator in most cases was segmental demyelination at the root entry zone of the trigeminal nerve. Some of the recognized causes included vascular compression of the nerve, a compressive mass lesion, postinfectious multiple sclerosis, trigeminal deafferentation, and atypical facial pain that may be related to a somatoform pain disorder. Traditionally, medical therapy is the initial treatment of choice. If the condition becomes medically refractory, various surgical options are described and are available, some with better success rates than others.
Evolution of Therapies for Trigeminal Neuralgia
Medical management
Early medical treatments for the treatment of TN in the 18th and 19th centuries included such compounds as quinine derived from Peruvian bark, mercury, opium, arsenic, and powder of gelsenium. Trichloroethylene and stilbamidine became popular choices for the treatment of facial pain in the early 20th century; however, their side-effect profile precluded them from becoming lasting options. The use of antiepileptic medications was first described in 1942 by Bergouignan with the introduction of sodium diphenylhydantoin. By the 1960s, phenytoin and, subsequently, carbamazepine were largely used as the treatments of choice as medical therapies for TN. Several other antiepileptic medications have been introduced to the treatment paradigm including lamotrigine, clonazepam, valproic acid, and even gabapentin. Currently, carbamazepine and oxcarbazepine are the first-line drugs of choice given a near 90% rate of efficacy with a more tolerable side effect-profile followed by phenytoin as a second-line agent.
Percutaneous Ablative Techniques
Percutaneous chemoneurolysis
Chemoneurolysis for the treatment of TN with the use of alcohol injections into peripheral nerves was first introduced by Schloesser in 1904. The side effects of this treatment, however, included temporary weakness of the muscles of mastication, transient anesthesia or paresthesias, and recurrence of TN after initial relief. Over the years, in an attempt to provide more lasting effects, more toxic or caustic agents were entertained for injection into the Gasserian ganglion, such as osmic acid, alcohol, and glycerol. Ironically, the discovery of glycerol as a potential treatment was developed by chance while using glycerol to introduce tantalum dust into the trigeminal cistern. This event led to the birth of percutaneous retrogasserian glycerol chemoneurolysis. However, all percutaneous procedures only yielded temporary relief with a higher likelihood of recurrence.
Percutaneous radiofrequency lesioning
Electrocoagulation of the trigeminal nerve was first described and attempted by Rethi in 1913. In 1931, Kirschner developed a stereotactic approach for insertion of an insulated needle through the foramen ovale for electrocoagulation of the Gasserian ganglion using monopolar cautery. Radiofrequency thermal lesioning of the preganglionic trigeminal rootlets was introduced in 1974 by Sweet and Wepsic. They combined various measures to control the current delivery including short-acting anesthetic drugs, electrical stimulation, and temperature monitoring and paved the way to improve the efficacy and safety of the procedure. Since their initial description of the technique, many prominent neurosurgeons such as Nugent, Rovit, and Tew and Taha have worked to further improve the approach, such as modifications in the electrode type that allowed for more selective lesioning of the sensory fibers of the nerve and the repetition of small, less dense lesions during one treatment session. Of all the percutaneous techniques, radiofrequency lesioning is associated with longer duration of pain relief. However, it also carries a higher risk of facial numbness, corneal anesthesia, keratitis, and anesthesia dolorosa. There is also a higher risk of complications for repeat procedures.
Percutaneous balloon microcompression
In 1983, Mullan and Lictor introduced percutaneous balloon compression of the Gasserian ganglion. The procedure involved threading a Fogarty balloon catheter into the foramen ovale and the trigeminal cistern. Inflation of the balloon caused mechanical injury to the trigeminal ganglion and the preganglionic rootlets. Initial complications included transient ipsilateral masseter and pterygoid muscle weakness. Mullan and Lictor’s technique was further refined in 1996 by Brown and colleagues, who developed the idea of using a blunt stylet following initial skin penetration to avoid vascular injury. However, despite the advances in the use of percutaneous balloon compression, several limitations exist, including bradycardia and brief hypotension caused by the trigeminocardiac reflex, postoperative numbness, and temporary weakness in the muscles of mastication, which can occur in up to 66% of patients.
Stereotactic Radiosurgery
Initial efforts at irradiation of the Gasserian ganglion in the 1890s yielded disappointing results. In 1971, Lars Leksell used stereotactically focused radiation targeted to the trigeminal ganglion in order to treat a small number of patients with trigeminal neuralgia. However, with the advent of stereotaxis and better targeting over time at the dorsal root entry zone, retrogasserian gamma knife surgery (GKS) has become a safe and efficacious modality for the treatment of TN for both first- and second-line treatment given its low side-effect profile, avoidance of open surgery, and patient satisfaction. This involves using photon energy to create a destructive lesion using focused radiation to injure the sensory root. Although initial pain relief can be achieved in up to 90% of cases, patients typically do not experience immediate posttreatment pain relief because of a lag time ranging from 1 to 3 months. One of the side effects is facial numbness, ranging from 20% to 32%. One of the challenges of GKS is the long-term durability of pain relief. In a study by Dhople and colleagues, freedom from pain goes down by 50% by 5 years. With a median follow-up of 5.6 years in 102 patients treated with GKS, 64% remained pain free and off medications, whereas 19% remained in severe pain with inadequate pain control. Nevertheless, GKS for TN may be the procedure of choice for nonsurgical candidates or patients with multiple medical comorbidities for whom open surgery carries increased risk.
Open Surgical Management of Trigeminal Neuralgia
Nerve sectioning
Treatments for TN have existed for as long as the condition itself was recognized. Surgical treatment directly targeting the trigeminal ganglion was first reported by Carnochan in 1858. Carnochan’s theory was further refined over the next few decades by various surgeons from around the world, namely Rose in London ; Andrews in Chicago ; and Horsley, Taylor, and Coleman. In 1892, Hartley ( Fig. 2 A ) and Krause ( Fig. 2 B) independently described an extradural, subtemporal, middle fossa approach for Gasserian ganglionectomy. Through the Hartley-Krause approach, the nerves were divided at the foramen ovale and the foramen rotundum and excised to a point back beyond the Gasserian ganglion ( Fig. 3 ). Spiller and Frazier further refined this technique by sparing the upper portion of the ganglion and the first branch of the trigeminal nerve to decrease the risk of corneal ulceration. In 1921, Frazier declared that “the problem of trigeminal neuralgia had been mastered.”
By 1928, Cushing, Frazier, and Stookey had all advanced the technique by selectively sectioning only the affected fibers in the dorsal trigeminal root. Thus the Spiller-Frazier procedure became the established and preferred surgical treatment for TN for close to 50 years. Although it was associated with an astonishingly high rate of facial paralysis and the feared complication of keratitis, many of the great neurosurgeons of the day hailed it as a safe and effective procedure. In this early era of neurosurgery, any procedure shown to be moderately effective with “acceptable” risks was quickly adopted. At the time, most neurosurgical operations still carried about a 50% risk of mortality. Therefore, when Spiller and Frazier revealed their operation was associated with little morbidity and decent outcomes, it was rapidly accepted.
Walter Dandy ( Fig. 4 ), however, was not particularly convinced of the effectiveness of the Spiller-Frazier approach. Having done hundreds of such cases, he found that facial paralysis, facial anesthesia, and other serious complications were occurring too often. During the 1920s, Dandy developed a suboccipital, cerebellar surgical approach ( Fig. 5 ), which involved complete or partial sectioning of the sensory root of the trigeminal nerve within the posterior fossa instead of the middle fossa ( Fig. 6 ). Dandy emphasized the importance of locating the junction of the transverse and sigmoid sinuses and obtaining an adequate dural exposure to approach the fifth cranial nerve. Initially, Dandy performed a complete neurectomy of the sensory root. Later, through experimentation, he modified his technique to perform only a partial sectioning of the root (see Fig. 6 ). He found that this technique allowed for the retention of sensation to touch. Even more important to Dandy was that the operation was “relatively bloodless” and had a much lower risk of facial paralysis as the approach targeted the furthest part of the Gasserian ganglion from the facial nerve and trigeminal motor root.
