Temporalis Muscle Suspension on Synthetic Cranioplasty: Technical Note

Temporal hollowing is a disfiguring complication after a craniectomy operation resulting from temporalis muscle atrophy, contraction, and adhesion to the underlying dura. We describe a technique for temporalis muscle re-suspension utilizing multi-hole cranial plates and screws to recreate the superior temporal line on an otherwise smooth synthetic cranioplasty implant


Introduction
Temporal hollowing can be a disfiguring complication after a craniotomy or craniectomy operation, and is associated with poor temporalis muscle function and temporomandibular joint pain [1][2][3]. This cosmetic and functional disfigurement involving the temporalis muscle is exacerbated after hemi-craniectomy, commonly utilized in patients with traumatic brain injury or large ischemic stroke. The large skull defect frequently leads to temporalis muscle atrophy, contraction, and adhesion to the underlying dura over the weeks to months before cranioplasty. Separating the muscle from the dura at the time of cranioplasty is difficult and creates more muscle ischemia and scarring. Often, the native bone flap is either lost or discarded due to an infection; this subsequently requires the use of a synthetic cranioplasty implant to repair the skull defect. Temporalis re-suspension is uniquely challenging with a synthetic implant versus native bone, where a cuff of tissue along the superior temporal line is often left behind to suture the muscle to at the time of cranioplasty. Custom implants can produce an excellent cosmetic result with restoring the bony defect to the original contour of the skull; however, temporal hollowing can undermine these results if adequate attention is not given to re-suspension of the temporalis muscle. In order to achieve this, the temporalis muscle must be dissected off the dura and re-suspended on the synthetic cranioplasty implant. Numerous techniques have been described for suspension of the temporalis muscle after craniotomy or craniofacial reconstruction, including suturing to microscrews, plates, holes drilled in the bone, or a myofacial cuff, all associated with satisfactory results [4][5][6][7][8][9][10]. In this technical note, we describe an adaptation of these techniques for suspension of the temporalis muscle using multi-hole plates to re-create the superior temporal line on a smooth synthetic cranioplasty implant that optimizes cosmesis, and improves the function of the temporalis muscle.

Technical Report
The UCSF Committee on Human Research does not require approval for case studies including up to three individuals. Informed patient consent was obtained.
A 27-year-old man, with a history of a previous right-sided hemi-craniectomy for an epidural hematoma after falling from a height of two stories (Figure 1), was taken to the operating room three months after his initial injury for implantation of a custom synthetic cranioplasty implant. After elevation of the scalp, the temporalis muscle was dissected off the underlying dura. The cranioplasty was inserted and fixed to the skull with titanium plates. These plates were recessed, to prevent erosion through the skin, by drilling a small groove in both the implant and the skull. The superior temporal line was recreated by fixing two long plates on the synthetic implant with screws. The temporalis muscle was then attached to these plates with 2.0 vicryl sutures spaced approximately 1 cm apart (Figure 2). At two months follow-up, the patient was pleased with the cosmetic results. He was noted to have minimal temporal hollowing and symmetric jaw movements ( Figure 3).

Discussion
Temporal hollowing is a disfiguring complication after a craniectomy operation resulting from temporalis muscle atrophy, contraction, and adhesion to the underlying dura. We describe a technique for temporalis muscle re-suspension utilizing multi-hole cranial plates and screws to recreate the superior temporal line on an otherwise smooth synthetic cranioplasty implant. In conjunction with a custom-made implant, this technique can optimize cosmetic and functional outcomes in patients who are at high risk for disappointing and disfiguring cosmetic results. Further, proper re-implantation of the muscle may also lead to improved function for chewing and symmetry of jaw opening and closure.

Conclusions
Special attention must be paid to re-suspension of the temporalis muscle at the time of cranioplasty to avoid disfiguring cosmetic results and poor function. Re-creation of the superior temporal line on a smooth synthetic custom implant, as described in this report, has produced favorable results in the senior author's 10 year experience (approximtely 40 cases) with this technique.