ECHN PNST are rare benign tumors that commonly arise at the head and neck region. Although most patients with ECHN PNST are asymptomatic, rapid growth or neurologic deficits require definitive treatment in order to avoid further compression and subsequent ischemia of adjacent nerve fibers. Preoperative diagnostic imaging studies are essential for planning the optimal surgical approach and for determining the extent of surgical resection. There are two main approaches: complete tumor excision (en bloc resection) and intracapsular resection [3], and the risks and benefits of each need to be weighed according to the individual case [6]. In general, complete resection may ensure lower recurrence rates but it usually results in neural compromise, while intracapsular resection is a nerve-sparing technique but it bears the risk of residual or recurrent disease.

We assessed the functional outcomes of patients who underwent excision of ECHN PNST. Most of the patients in our cohort who underwent surgical resection of a cervical or parapharyngeal PNST (Table 2) were operated by means of a nerve-preserving technique. Intracapsular resection was guided by neural monitoring and an operating microscope for microdissection and preservation of functional nerve fibers. Outcomes were dependent upon several variables, including the location and size of the lesion and the ability to apply nerve stimulation during intraoperative monitoring.

Preservation of nerve function is challenging when the sympathetic chain is involved [7]. Both of the patients with sympathetic chain schwannomas in our cohort displayed ptosis and miosis after surgery. When the brachial plexus is the nerve of origin, preoperative neurologic deficit or neuropathic pain portends poorer functional outcomes, even with the use of intraoperative neural monitoring, however due to its functional significance, the intracapsular approach shall be the treatment of choice. We observed that excisions of cervical PNST originating from other nerves, less commonly resulted in postoperative neurologic deficits when applying the intracapsular resection technique. In our experience, the use of an intraoperative microscope and electrophysiologic monitoring resulted in nerve function preservation in nine out of 15 cases (60%). The nerve-preserving approach resulted in good functional outcomes without significant neural compromise compared to en bloc resections that unavoidably compromise nerve function by complete nerve transection. Notebly, even outside the cervical and brachial plexuses, nerve function preservation with intracapsular resection was successful in 5 out of 9 cases corresponding to 55%.

Patients with a solitary ECHN PNST should be considered as being at low risk of malignancy, although reports on recurrence rates are limited [7, 9]. No recurrences were documented among the patients in our cohort, while residual tumor was observed in one patient who underwent intracapsular resection.

We acknowledge the limitations of our study. This is a limited-number retrospective cohort of patients, underpowered to draw any statistically significant conclusions. Only minority of patients adhered to surveillance paradigm following the first year after surgery, noted by the median 1 year of follow up. This greatly limits recurrence rate determination. Still, this is one of the largest cohorts reporting the results of intracapsular microdissection of PNST in the head and neck region. Our data provide useful information for counseling patients considering definitive surgical resection for ECHN PNST about the potential function sparing. Longer follow-up studies are warranted, with timely imaging studies looking at the recurrence rates after surgical resection.

In conclusion, considering the benign nature of ECHN PNST, expectant observation may be suitable for asymptomatic patients. However, when surgery is required, intracapsular resection and intraoperative nerve monitoring may reduce complications and preserve functionality, especially when neuronal function has not been compromised by the tumor.