Unilateral forehead paralysis following operative repair of facial trauma: a case study and review of the literature.
The anatomy, function, and course of the temporal branch of the facial nerve are critical to the development of a surgical plan. The temporal nerve provides motor innervation to the frontalis, corrugator, and lateral orbicularis oculi muscles. (2) These muscles are important for facial expression, and loss of muscle function can have very damaging effects on the patient's psyche, self-confidence, and social interaction, and can ultimately lead to depression. (3) The longer a muscle is denervated, the more the probability of reinnervation decreases, indicating the need for early evaluation, including exploration of the temporal nerve, to expedite the treatment plan and potentially improve outcomes. The risk of the exploratory surgery in certain cases is outweighed by the benefits of returning complete motor function and maintaining normal social interaction.
The temporal branch of the facial nerve is commonly injured in trauma due to its location and superficial course along the temporal region. (1) An illustrative depiction of the facial nerve is shown in Figure 1. This case involved the most superior branch, known as the temporal nerve. While the typical course of the facial nerve after exiting the stylomastoid foramen is presented, there is potential for anatomical variation in each patient. As shown, the temporal nerve branch exits the parotid gland anteriorly, and then branches into two to four rami at the inferior border of the zygomatic arch. (4,5,6) The arborization pattern is commonly grouped into posterior, middle, and anterior divisions of the temporal nerve. The rami will ascend superomedially to innervate the lateral orbicularis oculi, frontalis, and corrugator muscles. (2)
A 22-year-old male sustained a penetrating trauma to his left temporal fossa with needle nose pliers. Injuries included a burst stellate laceration, subdural hematoma, and temporal bone skull fracture. He was transported to a Level 2 Trauma Center, where a neurosurgeon performed an exploratory craniotomy to reduce and stabilize the fractured skull with a titanium plate.
Four weeks after the trauma the patient presented with complete left temporal branch palsy with inability to activate his left frontalis muscle (Figure 2a). It was not clear if the palsy was present at the time of injury. An electromyography and nerve conduction studies of Cranial Nerve VII and its innervated muscles revealed severe active denervation in the left frontalis muscle and severe partial denervation in the procerus muscle. The results of the study suggested axonotmesis, axon and myelin sheath disruption, of select branches of the left temporal nerve. With axonotmesis, the Schwann cell, the epineurium, and perineurium remain intact. (7)
Exploratory surgery was performed to evaluate the temporal nerve and correct the possible defect six weeks after the initial trauma. The temporal nerve was identified and neurolysis proceeded, starting at the distal position and carefully working proximally along the course of the nerve. A nerve stimulator was utilized to guide the dissection and identify intact motor branches of the facial nerve. At the level of the parotid gland, a silk suture was identified spot compressing the nerve (Figure 3a). The suture obstruction was removed, and there was no other disruption of the nerve identified. (Figure 3b). Approximately three months postoperative, the patient reported with 50% motion of the left brow with a moving Tinel's sign, in which tapping distally produces a tingling sensation over the nerve distribution. At six months postoperatively the patient reported full recovery of motion (Figure 2b).
The decision to provide surgical intervention for the treatment of temporal nerve palsy will be highly dependent on the chance of spontaneous recovery. (8) Seventy to eighty percent of patients diagnosed with Bell's Palsy will have some spontaneous recovery. However, palsy caused by viral infection or trauma will have a lower chance of spontaneous recovery. (8) While MRI is only indicated for facial nerve lesions of the brainstem, cerebellopontine angle, and intratemporal locations, EMG may aid in clinical decision making for superficial facial nerve lesions. (8) EMG results indicating severe denervation may prompt physicians to either wait for spontaneous improvement or perform exploratory surgery. One study showed that patients with normal EMG results had an 80% chance of full recovery. Patients that showed slight paresis had a 25% chance of full recovery, and patients that lacked excitability on EMG had almost no chance for full recovery. (9) Delayed exploration after an EMG indicating slight paresis allows time for the palsy to improve spontaneously, but delay could result in a less favorable outcome in cases of more severe denervation.
More involved procedures may be needed if surgical exploration is delayed or unsuccessful. A primary coaptation of the temporal nerve can be performed with patient outcomes that are aesthetically and functionally pleasing, but this option is most effective in the first 2 months of paralysis. (10) The primary repair is effective if both stumps of the nerve are available, the end musculature is still sustainable, and the gap in the nerve is less than 1 centimeter. (8,10) When there is a gap of over 1 cm, a graft will need to be harvested to ensure a tension free coaptation. (8) After approximately six months to one year of paralysis, the motor end plate of the muscle has a decreased capacity for reanimation, and more drastic repair techniques are indicated. (8,11) The temporalis muscle can be transposed locally to reanimate the upper and lower eyelids. (8) A free muscle transfer can also be used in muscle reanimation, first using a cross-facial nerve graft and then fixating the neurovascular anastomosis of the transplanted muscle. (8,11) However, the results for both procedures are less than optimal. There can be aesthetic changes to the facial area, and the muscles themselves must be retrained to achieve desired function. (8)
Temporal nerve injuries can be devastating for patients. Conservative logic suggests monitoring for spontaneous reanimation. However, without reanimation, the delayed surgical correction could lead to less than optimal patient outcomes. The implementation of early exploration, especially after trauma or surgery, can be beneficial in obtaining full recovery.
Students, West Virginia University School of Medicine, Morgantown, WV
W. Thomas McClellan MD, FACS
Plastic and Reconstructive Surgery, West Virginia University, Morgantown W. Va.
Corresponding Author: Dr. McClellan, Morgantown Plastic Surgery Associates, 1085 Van Voorhis Road, Suite 350, Morgantown, W.Va. 26505. Email: email@example.com.
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|Author:||Domico, Adam; Kurian, Susan; Davis, Meghan; Fazi, Alyssa; McClellan, W. Thomas|
|Publication:||West Virginia Medical Journal|
|Article Type:||Case study|
|Date:||Sep 1, 2015|
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