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of the nerve, its vascular supply, or structures surrounding Table 1: Location, cause, and type of nerve damage
the nerve during surgery. [7‑9] The placement of semi‑rigid during BSSO
fixation plates and screws may also cause nerve damage Location Cause Type of lesion
either directly or via compression of the nerve between Spyx Retractors Compression
bony segments after screw fixation.
Osteotomy Chisels, compression bony Compression,
Inferior alveolar nerve‑related neuropathic pain following area surfaces, freeing nerve, crushing,
iatrogenic damage to the nerve is a disabling condition screws, piezo, drill, saw transection
that severely affects the quality of daily life. [10‑12] This review Lower border Partial or total transection Drill, saw, piezo
covers the current knowledge regarding neuropathic pain BSSO: Bilateral sagittal split osteotomy
after BSSO and its incidence, pathophysiology, risk factors,
management, and steps for prevention. the ascending ramus during a horizontal osteotomy cut,
the bone cut at the lower border of the mandible, the
NEUROPATHIC PAIN AFTER BILATERAL connecting bone cut between the lower border and the
SAGITTAL SPLIT OSTEOTOMY buccal osteotomy of the mandibular body, with chiseling
during the sagittal split, between bone fragments after the
Incidence bony movement, during placement of the osteosynthesis
No single accurate value appears to be available for the material and during insertion of an osteosynthesis screw.
overall prevalence of neuropathic pain. The development Grades of nerve injury are categorized into neuropraxia,
of chronic pain after surgery is fairly common, with axonotmesis, or neurotmesis, depending on the extent of
estimates ranging from 10% to 50% after many common the damage. In clinical settings, various combinations
[25]
operations. The pain may be severe in 2‑10% of these of nerve damage can coexist, giving rise to a variety of
[13]
patients and is usually considered to be neuropathic. [14,15] sensory dysfunctions. After a peripheral nerve lesion,
aberrant regeneration may occur. In some patients,
[26]
Information about neuropathic pain following orthognathic neurons become unusually sensitive and develop a
surgery is sparse. [16,17] Borstlap et al. prospectively
[18]
followed 222 patients after BSSO surgery and reported spontaneous pathological activity, abnormal excitability,
no incidence of neuropathic pain. The reported incidence and heightened sensitivity to chemical, thermal, and
mechanical stimuli. Persistent pain or neuropathic
of neuropathic pain in the literature after mandibular pain such as allodynia, and pain and discomfort with
osteotomies is less than 1% while the reported incidence occlusion [27,28] can occur.
in patients with iatrogenic IAN injuries during BSSO can
be as high as 45%. Marchiori et al. reported seven cases
[19]
of neuropathic pain among 1671 patients after BSSO, CLINICAL CHARACTERISTICS OF
for an incidence of 0.42%, while Politis et al. reported NEUROPATHIC PAIN
[20]
6 cases of neuropathic pain from 900 BSSOs with an
incidence of 0.67%. The main features of neuropathic pain include constant
pain, which can be superficial or deep, sharp or aching,
Other reports [16,21] describe an incidence as high as 5% lancinating pain (i.e. sudden and sharp, severe bursts of
of neuropathic pain among patients who sustained pain), and allodynia (i.e. pain experienced after normally
peripheral trigeminal nerve injuries after sagittal split nonpainful stimuli, like light touch). The discomfort
ramus osteotomy. Teerijoki‑Oksa et al. prospectively is usually of a chronic nature and may be described by
[22]
followed 19 patients after BSSO surgery and found a 5% the patient as a burning sensation, a sharp, stabbing, or
overall occurrence of neuropathic pain at 1‑year follow‑up, shooting pain, or “like an electric shock”. [20]
which is similar to the overall estimated incidence of
neuropathic pain after traumatic and iatrogenic nerve The complaints often seem to be out of proportion to the
[23]
[21]
injuries. Jääskeläinen et al., on the other hand, pain that would be expected to accompany the original
found a 45% incidence of neuropathic pain in 58 patients injury. [3,19] Neuropathic pain resulting from axonal nerve
with iatrogenic sensory deficits of the IAN and lingual injury is often associated with crushing or stretching
[20]
nerve (LN). nerve injuries rather than total nerve transaction.
Other characteristics of neuropathic pain include a lack
Microsurgical repair of a damaged IAN after orthognathic of response to anti‑inflammatory pain killers (nonsteroidal
surgery does not alleviate neuropathic pain if the latter anti‑inflammatories, paracetamol), improved symptoms in
was present before the repair. Furthermore, it does the mornings, minimal sleep disturbance, and worsening
not cause neuropathic pain if the pain was not present during the day or with stress, fatigue, and illness.
beforehand. [17]

Mechanism of nerve damage RISK FACTORS FOR NERVE DAMAGE
The IAN is at significant risk in all stages of AND NEUROPATHIC PAIN
surgery [Table 1], and nerve manipulation during BSSO
is a known risk factor for nerve injury. This nerve can The proximity of the mandibular canal to the lower border
[24]
be damaged at the following points: the spyx during the of the mandible is an important factor in self‑reported
placement of a retractor posterior to or above the lingual, hypoesthesia of the lower lip. The exposure and
[27]
172 Plast Aesthet Res || Vol 2 || Issue 4 || Jul 15, 2015