Transient facial nerve paralysis in two patients following zygomaticotemporal nerve block - Case studies

Dear Editor,

Zygomaticotemporal nerve blocks are routinely performed for craniofacial pain disorders and as a component of scalp blocks for perioperative analgesia.[1] We report transient facial nerve paralysis following zygomaticotemporal nerve blocks in two patients.

A 65-year-old man with carcinoma right buccal mucosa involving the right temporal region presented with severe pain [numerical pain rating score (NRS) of 8/10]. A landmark-guided zygomaticotemporal nerve block was performed using a 1.5 ml mixture of bupivacaine 0.5% and 20 mg of triamcinolone with a 23G needle.[1,2] The patient reported immediate relief of pain (NRS 2/10). However, over the next 5 min, the patient was not able to close his right eye completely and wrinkle his forehead. There was a loss of palpebral folds on his right forehead [Figure 1a]. A diagnosis of lower motor neuron palsy of the facial nerve was made. Facial paralysis resolved completely in 5 h.

Figure 1.

(a) Picture shows inability to close the right eye and flattening of forehead creases in the first patient administered right zygomaticotemporal block. (b) Illustrates close anatomical proximity of auriculotemporal nerve, frontotemporal branch of facial nerve and zygomaticotemporal nerve. (c) Coronal cross section illustration of the temporal region. The frontotemporal branch of fascial nerve is seen traversing from deep to superficial planes above the zygomatic arch. The intended plane for landmark-guided block of zygomaticotemporal nerve in the intermediate fat pad is well illustrated. DLDTF = deep layer/lamina of the deep temporal fascia, DTF = deep temporal fascia, DTFP = deep temporal fat pad, FTBFN = frontotemporal branch of the facial nerve, ITFP = intermediate temporal fat pad, SLDTF = superficial layer/lamina of the deep temporal fascia, STFP = superficial temporal fat pad, TPF = temporoparietal fascia, ZTN = zygomaticotemporal nerve

Another 49-year-old male developed a post-traumatic headache in the left anterior temporal region (NRS 7/10) and complained of an inability to close his left eye, 5 min after landmark-guided zygomaticotemporal nerve block with a 1.5 ml mixture of bupivacaine 0.5% and 20 mg of triamcinolone. This patient also had a complete recovery in 4 h.

Three months follow-up was satisfactory in both patients, with an NRS of 3/10 and no residual abnormality.

The temporal region is supplied primarily by the zygomaticotemporal nerve anteriorly and the auriculotemporal nerve posteriorly[2] [Figure 1b and c]. Both these nerves are liable to be involved in various pathologies, leading to intractable headaches. The frontotemporal branch of the facial nerve [Figure 1b and c] supplies the frontalis, orbicularis oculi and corrugator supercilii muscles. Injury to this nerve may result in an inability to close the eye completely, a flattened forehead and eyebrow ptosis.[2]

Transient paralysis of the facial nerve has been observed commonly following a scalp block for craniotomies. However, despite the concurrent blockage of the zygomaticotemporal nerve, this has traditionally been attributed to the blockage of the auriculotemporal nerve.[1,3,4] Cadaveric studies have demonstrated communication between the zygomaticotemporal nerve and the frontotemporal branch of the facial nerve.[5] In a similar case, Strauss et al.[6] reported complete left facial nerve palsy following blockade of the left greater and lesser occipital nerves on using a landmark technique in a patient with occipital neuralgia. This was attributed to the interneural connections of the posterior auricular branch of the facial nerve with the greater and lesser occipital nerves. The possibility of drugs being deposited along or inadvertently tracking along the tissue planes to the communicating branches between the frontotemporal nerves and the zygomaticotemporal nerve, in addition to aberrant spread in undesired tissue planes cannot be ruled out in our cases.

Zygomaticotemporal nerve blocks can be further made safer by discussing the risks of paralysis of the frontotemporal branch of the facial nerve before the procedure and following standard precautions such as aspiration and slow injection of lower volumes.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms from both the patients. In the form, the patients has given consent for images and other clinical information to be reported in the journal. The patient understands that their name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.