Botulinum toxin A for management of refractory concurrent buccal and inferior alveolar nerve post-traumatic neuropathies: a case report

Abstract

Painful post-traumatic trigeminal neuropathy (PPTTN) can result from iatrogenic injury to one or more branches of the trigeminal nerve during oral surgical procedures such as tooth extractions. Like other chronic neuropathic pain conditions, PPTTN can significantly alter the patient's quality of life, especially when pharmacological treatment is ineffective or not tolerated. As such, new treatment options have been investigated, including local injections of botulinum toxin type A (BTX-A). A 29-year-old woman presented to our tertiary orofacial pain clinic for evaluation of chronic electric shock-like pain attacks and severe allodynia in the territory of the right inferior alveolar nerve and buccal nerve following right mandibular third molar extraction 3 years prior. Following several failed attempts at classic pharmacological management (including carbamazepine, venlafaxine, duloxetine, pregabalin, clonazepam, and amitriptyline), BTX-A injections were administered in the vicinity of the right mental nerve. This treatment provided significant improvement in the patient's condition and overall quality of life with no significant adverse effects. Because both neuropathies were significantly improved by remote BTX-A injections, this case report provides preliminary clinical evidence supporting spinopetal transport of BTX-A, as shown in animal models, as an underlying pathophysiological mechanism of BTX-A-mediated analgesia.

Keywords: Painful post-traumatic trigeminal neuropathy; botulinum toxin type A; buccal nerve; facial pain; inferior alveolar nerve; spinopetal transport.

Figure 1.

Clinical view of the territory of intraoral buccal mucosa allodynia, mapped using a dermographic marker pen. This territory of allodynia was compatible with the innervation territory of the buccal nerve (see Reference 23 for comparison).

Figure 2.

Postoperative coronal (left) and sagittal (right) cone-beam computed tomography images of the socket of the right mandibular third molar 1 month after extraction. Note the burr-shaped lingual cortex destruction (arrows) in the immediate vicinity of the inferior alveolar nerve bundle (circle), suggestive of iatrogenic injury.

Figure 3.

Clinical preoperative view of the botulinum toxin A injection in the vicinity of the right mental nerve bundle.

Figure 4.

Coronal (left) and sagittal (right) cone-beam computed tomography images (same as Figure 2) centered on the right mental foramen (arrows).

Figure 5.

Graphical representation of the analgesic effect of botulinum toxin A injections on spontaneous pain (self-reported by the patient on a 0 to 10 NRS), with separate evaluations for the inferior alveolar nerve territory (blue line) and buccal nerve territory (orange line). NRS = numerical rating scale.

Figure 6.

Didactic illustration of the putative innervation of the patient’s labiomental region using a surface three-dimensional reconstruction of the patient’s cone-beam computed tomography volume. Putative innervation was conjectured based on the reported topography of analgesia following the first and second botulinum toxin A injections.