Application of purified botulinum type a neurotoxin to treat experimental trigeminal neuropathy in rats and patients with urinary incontinence and prostatic hyperplasia

Therapeutic Efficacy of Botulinum Toxin in Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a unilateral, paroxysmal, sharp, shooting, or jabbing pain that occurs in the trigeminal nerve divisions, including the ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves. Typically, an episode is triggered by anything touching the face or teeth. TN is a clinical diagnosis with no specific diagnostic test; it is determined by the patient's medical history and pain description. Imaging is necessary to exclude secondary causes. The precise reason for TN is uncertain, but it is commonly believed to result from vascular compression of the trigeminal nerve root, typically near its origin in the pons. There are numerous surgical and medical treatment options available. The most frequently applied medical treatment therapies are carbamazepine and oxcarbazepine. Surgical alternatives are reserved for patients who do not respond to medical treatment. Botulinum toxin A (BTX-A) has emerged as a novel and promising alternative to surgery for individuals whose pain is unresponsive to medication. Multiple studies have established the safety and usefulness of BTX-A in treating TN, with the most significant benefits occurring between six weeks and three months after the surgery. This article reviews various studies published in the last 10 years regarding the therapeutic use of BTX-A in TN. These studies include various observational, clinical, pilot, and animal studies.

Botulinum neurotoxin type A alleviates mechanical hypersensitivity associated with infraorbital nerve constriction injury in rats

We investigated the effect of botulinum neurotoxin type A (BoNT-A) on mechanical allodynia and hyperalgesia associated with infraorbital nerve constriction (ION-CCI) in rats. ION-CCI rats received a subcutaneous BoNT-A injection into the whisker pad area on day 7 postoperatively and underwent pain assessment on days 14 and 21 postoperatively. Rats were assigned to one of four treatment groups (n=5 each): ION-CCI+BoNT-A 20pg (low-dose group), ION-CCI+BoNT-A 200pg (high-dose group), ION-CCI+saline, and Sham. Mechanical allodynia and hyperalgesia were evaluated preoperatively (baseline) and on days 7, 14, and 21 postoperatively. After noxious mechanical stimulation of whisker pad skin, the number and distribution pattern of the phosphorylated extracellular signal-regulated kinase (pERK)-immunoreactive (IR) neurons were analyzed in the trigeminal spinal subnucleus caudalis (Vc) and upper cervical spinal cord (C1-C2). On day 21, nocifensive behavior was attenuated by high-dose but not low-dose BoNT-A administration. In addition, after noxious mechanical stimulation of whisker pad skin, the numbers of pERK-IR cells in the superficial laminae of Vc and C1-C2 were significantly lower in the high-dose BoNT-A group than in the ION-CCI+saline group. The present findings suggest that, by suppressing Vc neuronal activity, high-dose intradermal injection of BoNT-A at the site of ION innervation alleviates mechanical facial allodynia and hyperalgesia associated with ION-CCI.