Anatomical landmarks for localizing the otic ganglion: A possible new treatment target for headache disorders

Abstract

Background: The otic ganglion (OG) is a cranial parasympathetic ganglion located in the infratemporal fossa under the foramen ovale (FO) and adjacent to the medial part of the mandibular nerve. Parasympathetic innervation of intracranial vessels from the OG has been shown both in animal and human models and evidence suggests that the OG plays an important role in the cranial vasomotor response. We review the evidence that positions the OG as a viable target for headache disorders. The OG is a small structure and not detectable on medical imaging. The FO is easily identifiable on CT scans and the mandibular nerve on MRI, hence, the position of the OG may be predicted if the mean distance from the FO is known. Objective: The objective is to describe the average distance between the FO and the OG in a sample of 18 infratemporal fossae from 21 cadavers. Methods: A total of 21 high definition photographs of 21 infratemporal fossae from 18 cadavers were analyzed. The distance between the inferior edge of the medial part of the FO to the OG was measured. Results: Four photographs of infratemporal fossae of four cadavers were excluded due to the inability to localize the inferior edge of the FO. A total of 15 infratemporal fossae from 17 cadavers were measured. The mean distance from the FO to the OG was 4.5 mm (SD 1.7), range 2.1-7.7 mm. Conclusions: We have described the average distance from the OG to an easily identifiable anatomical landmark that is visible in CT scans, the FO. This anatomical study may aid in the development of strategies to localize the OG in order to explore its role as a therapeutic target for headache disorders.

Open‐Label, Multi‐Dose, Pilot Safety Study of Injection of OnabotulinumtoxinA Toward the Otic Ganglion for the Treatment of Intractable Chronic Cluster Headache

“…These 2 structures are easily identified on fused MRI and CT‐scans. It has been described that the OG is consistently located immediately medial to the mandibular nerve 8 and its distance to the foramen ovale has also been documented 1 . Currently, there are no biomarkers to confirm target engagement with the OC and we can, therefore not exclude a lack of target engagement.…”

“…The otic ganglion (OG) has been introduced as a possible target in trigeminal autonomic cephalalgias 1 . Cluster headache (CH) is the most common of the trigeminal autonomic cephalalgias 2,3 with a significant impact on the sufferer's quality of life and no approved treatments for its chronic form 4 …”

“…It has been hypothesized that the trigeminal autonomic reflex loop is more complex than previously thought 1 . The efferent part of this loop, in addition to the projections toward the SPG, might involve another efferent pathway; fibers from the inferior salivatory nucleus, which project to the OG.…”

“…It is situated directly medial to and in contact with the mandibular nerve 8 . The mean distance from the OG to the foramen ovale (a structure localizable on head computed tomography (CT) scans) is 4.5 mm (SD 1.7) 1 . Some important nearby structures are the middle meningeal artery, maxillary artery, lingual nerve, and inferior alveolar nerve.…”

Identification of cranial nerve ganglia using sectioned images and three-dimensional models of a cadaver

“…The first step was to identify all 12 pairs of the ganglia of the cranial nerves: the ciliary ganglion, trigeminal ganglion, pterygopalatine ganglion, otic ganglion, submandibular ganglion, geniculate ganglion, vestibular ganglion, spiral ganglion, superior and inferior glossopharyngeal ganglia, and superior and inferior vagal ganglia (Table 1) [12][13][14][15][16][17][18][19][20][21][22][23]. For this, sectioned images of the brainstem were examined to determine the origins of the cranial nerves (Fig.…”