Ipsilateral Limb Extension of Referred Trigeminal Facial Pain due to Greater Occipital Nerve Entrapment: A Case Report

Abstract

We report a very rare case of referred pain associated with entrapment of the greater occipital nerve (GON) occurring not only in the ipsilateral hemiface but also in the ipsilateral limb. There is an extensive convergence of cutaneous, tooth pulp, visceral, neck, and muscle afferents onto nociceptive and nonnociceptive neurons in the trigeminal nucleus caudalis (medullary dorsal horn). In addition, nociceptive input from trigeminal, meningeal afferents projects into trigeminal nucleus caudalis and dorsal horn of C1 and C2. Together, they form a functional unit, the trigeminocervical complex (TCC). The nociceptive inflow from suboccipital and high cervical structures is mediated with small-diameter afferent fibers in the upper cervical roots terminating in the dorsal horn of the cervical cord extending from the C2 segment up to the medullary dorsal horn. The major afferent contribution is mediated by the spinal root C2 that is peripherally represented by the greater occipital nerve (GON). Convergence of afferent signals from the trigeminal nerve and the GON onto the TCC is regarded as an anatomical basis of pain referral in craniofacial pain and primary headache syndrome. Ipsilateral limb pain occurs long before the onset of the referred facial pain. The subsequent severe hemifacial pain suggested GON entrapment. The occipital nerve block provided temporary relief from facial and extremity pain. Imaging studies found a benign osteoma in the ipsilateral suboccipital bone, but no direct contact with GON was identified. During GON decompression, severe entrapment of the GON was observed by the tendinous aponeurotic edge of the trapezius muscle, but the osteoma had no contact with the nerve. Following GON decompression, the referred trigeminal and extremity pain completely disappeared. The pain referral from GON entrapment seems to be attributed to the sensitization and hypersensitivity of the trigeminocervical complex (TCC). The clinical manifestations of TCC hypersensitivity induced by chronic entrapment of GONs are diverse when considering the occurrence of extremity pain as well as facial pain.

Generalized Extension of Referred Trigeminal Pain due to Greater Occipital Nerve Entrapment

“…Te pain location in the submandibular area of the current case, which was difcult to explain, coincided with subauricular and submandibular areas known to be pain distribution areas of GON entrapment [18][19][20][21][22][23][24]. In addition, it has been reported that referred pain of chronic GON entrapment might extend not only to trigeminal distribution but also the arms and legs [26].…”

“…Te author's GON decompression technique using an oblique, paramedian approach using a microscope has already been reported [20][21][22][23][24][25][26]. In brief, it is a distal approach that frst addresses the distal branch of the GON that has passed through the trapezial canal.…”

“…It has been reported in recent years that chronic noxious aferent input from entrapment can result in sensitization and hypersensitivity of secondary neurons in the TCC, resulting in referred pain in the facial trigeminal distribution [20][21][22][23][24][25][26]. Referral to the orofacial area occurs not only in the V1 (ophthalamic) region but also in V2 (maxillary) and V3 (mandibular) regions.…”

“…Referred pain from GON entrapment has been reported to cause deep ear pain [24]. It might also extend to the ipsilateral arm and leg beyond the craniocervical region [26]. It has been confrmed that the referred facial trigeminal pain caused by GON entrapment can disappear with decompression of the GON [20][21][22][23][24][25][26].…”

“…It might also extend to the ipsilateral arm and leg beyond the craniocervical region [26]. It has been confrmed that the referred facial trigeminal pain caused by GON entrapment can disappear with decompression of the GON [20][21][22][23][24][25][26]. Tis report shows that referred pain with central sensitization due to GON entrapment can extend not only to the trigeminal nociceptive area but also to the whole body, which is the area of spinal nociception.…”