Sustained effect of repeated botulinum toxin type A injections in trigeminal neuralgia

Non-Migraine Head Pain and Botulinum Toxin

Botulinum toxin A (BT-A), a potential neurotoxin produced by the bacterium Clostridium botulinum, is known for its ability to prevent the release of acetylcholine at the neuromuscular synapse, leading to temporary muscle paralysis. BT-A is used for a wide range of therapeutic applications. Several studies have shown mechanisms beyond the inhibition of acetylcholine release for pain control. BT-A inhibits the release of neurotransmitters associated with pain and inflammation, such as glutamate, CGRP, and substance P. Additionally, it would be effective in nerve entrapment leading to neuronal hypersensitivity, which is known as a new pathogenesis of painful conditions. BT-A has been applied to the treatment of a wide variety of neurological disorders. Since 2010, BT-A application has been approved and widely used as a chronic migraine prophylaxis. Moreover, due to its effects on pain through sensory modulation, it may also be effective for other headaches. Several studies using BT-A, at different doses and administration sites for headaches, have shown beneficial effects on frequency and severity. In this review, we provide an overview of using BT-A to treat primary and secondary headache disorders.

Compared to oxcarbazepine and carbamazepine, botulinum toxin type A is a useful therapeutic option for trigeminal neuralgia symptoms: A systematic review

OBJECTIVES

This review aimed to compare the effectiveness of three treatments: BTX A, CBZ, and OXB, in managing trigeminal neuralgia (TN).

MATERIAL AND METHODS

We conducted a thorough search for research articles related to our issue using specific keywords on several databases, including Cochrane Central Register of Controlled Trials, Science Direct, Scopus, PubMed, Elsevier, Springer Journals, Ovid Medline, EBSCO, and Web of Science. Our focus was on publications from 1965 to 2023.

RESULTS

We retrieved 46 articles from the search and reviewed them carefully. Out of these, we selected 29 articles that met the inclusion criteria. Among the selected articles, 11 investigated the effects of CBZ and OXB, while 18 explored the impact of BTX A on the improvement of TN symptoms. The response rate ranged between 56% and 90.5% for CBZ and between 90.9% and 94% for OXB. The response rate for BTX A ranged between 51.4% and 100%. All these three treatments had a remarkable effect on the improvement of TN. Importantly, findings highlighted that side effects of CBZ and OXB could lead to treatment discontinuation in some cases, whereas BTX A's side effects have been minimal and less frequent.

CONCLUSIONS

Consequently, BTX A emerges as a promising alternative for TN treatment. However, additional clinical trials are necessary to validate this finding, and further research is required to establish a standardized protocol for administering BTX A in TN.

Significance of different offending vessels and development of a potential screening tool for trigeminal neuralgia

OBJECTIVES

This study was performed amongst trigeminal neuralgia (TN) patients with neurovascular contact (NVC) to 1) investigate the association of the demographic and radiologic factors/variables with TN occurrence, and 2) develop a screening tool for TN/TN-affected nerves based on the factors/variables associated with it.

METHODS

Eighty-five TN patients were recruited, and 121 trigeminal nerves with NVC were derived from them. Based on MRI sequences, including balanced turbo field echo and enhanced T1 high-resolution isotropic volume excitation, radiologic factors/variables for each nerve, from the offending vessel to the presence of nerve displacement, were identified by a neuroradiologist and a neurosurgeon. Demographic and clinical data were obtained from clinical notes. Logistic regression was performed to assess the association of the factors/variables with TN occurrence (i.e., affected vs. unaffected nerves).

RESULTS

Three factors/variables were significantly (p < 0.05) associated with TN occurrence amongst patients with NVC: nerve laterality, vertebral artery (VA) involvement, and the presence of nerve displacement. The nerves with VA involvement, those on the right side, and those with nerve displacement exhibited a significantly higher likelihood/odd of being affected by TN, compared to those without VA involvement, those on the left side, and those without nerve displacement, respectively. Based on these factors/variables, a screening tool/nomogram with acceptable accuracy was established (C-statistic/AUC = 0.80).

CONCLUSIONS

This study revealed an association of the three radiologic factors/variables with TN occurrence. A screening tool for TN/TN-affected nerves was established based on them. The findings may lay a foundation for an improvement of the diagnosis and clinical management of TN.

KEY POINTS

• VA involvement and nerve displacement could be identified using MRI, and are significantly associated with TN occurrence. • A potential objective screening tool/nomogram for TN/TN-affected nerves could be established based on the three radiologic factors/variables: VA involvement, the presence of nerve displacement, and nerve laterality. • The screening accuracy of the tool/nomogram is acceptable as the C-statistic is 0.80.

Neuromodulators for Atypical Facial Pain and Neuralgias: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the effectiveness of neuromodulating agents for the management of atypical facial pain and primary facial neuralgias.

METHODS

We searched MEDLINE, Embase, CINAHL, and ClinicalTrials.gov databases for original research articles that examine the effectiveness and adverse reactions of pharmacologic therapy for the treatment of trigeminal neuralgia and atypical facial pain. Studies that included surgical interventions for atypical facial pain or facial pain secondary to other causes were excluded. Meta-analysis was conducted for reductions in symptom scores and adverse effects.

RESULTS

Of 3,409 articles screened, 73 full-text articles were included, consisting of 45 observational studies and 29 randomized controlled trials. Twenty-four different pharmacological agents were assessed; carbamazepine was the most frequently studied while botulinum toxin A demonstrated the highest consistency in reduction of symptom scores. Pooled estimate of three randomized controlled trials revealed that patients with trigeminal neuralgia who received botulinum toxin A had higher odds (odds ratio 7.46; 95% CI 3.53-15.78) of achieving a ≥50% reduction in visual analogue scale scores compared to controls. Pooled estimate of 15 observational studies showed that three-fourths of patients with trigeminal neuralgia who received carbamazepine experienced clinically significant pain reduction (prevalence proportion 0.75; 95% CI 0.66-0.83).

CONCLUSIONS

Patients receiving botulinum toxin A for trigeminal neuralgia had higher odds of achieving ≥50% reduction in pain scores. A significant proportion of patients with trigeminal neuralgia experienced positive response to carbamazepine. There was moderate evidence for amitriptyline in patients with atypical facial pain. Standardization of outcome reporting would facilitate future quantitative comparisons of therapeutic effectiveness. Laryngoscope, 131:1235-1253, 2021.