J Oral Maxillofac Surg 46:124'134 .1990
Recovery of Neurosensory Function Following Orthognathic Surgery NESTOR D. KARAS, DDS,· SCOTT B. BOYD, DDS, PHD,t AND DOUGLAS P. SINN, DOS:f:
The purpose of this study was to prospectively define the recovery of touch discrimination following four commonly performed surgical procedures in 22 consecutive patients with no previous maxillofacial surgery. The surgical groups studied were Le Fort I osteotomy (LEFORT; n = 13), sagittal split ramus osteotomy (SSRO; n = 6), intraoral vertical ramus osteotomy (IVRO; n = 9), and isolated genioplasty (GENIO; n = 5). Neurosensory function was assessed by three different testing modalities which included static light touch (SLT), moving touch discrimination (MTD), and two-point discrimination (TPD). Cutaneous sensation of the lower lip and chin were examined for the mandibular procedures, whereas the infraorbital and upper lip regions were evaluated following maxillary surgery. Immediately following surgery, each group varied in both the incidence and magnitude of neurosensory deficits (NSD). The SSRO group had the highest percentage of sites with immediate postsurgical NSD to both SLT (72%) and MTD (67%), followed by the LEFORT (SLT = 50%, MTD = 58%), GENIO (SLT = 27%, MTD = 6%), and IVRO groups (SLT = 11%, MTD = 18%), respectively . Each group also varied in the severity of the initial postoperative deficit as measured by SLT, with the SSRO group showing the greatest deficit followed by the LEFORT, GENIO, and IVRO groups. During the 6-month recovery period each group approached preoperative levels of sensation at a different rate. The LEFORT group recovered most rapidly, with few anatomic sites showing NSD (SLT = 20%, MTD = 5%) at the 1-month postoperative examination, and the majority of the group (96%) returned to preoperative sensation by 3 months following surgery. The SSRO group recovered more slowly, with approximately half of the group demonstrating a deficit (SLT = 50%, MTD = 59%) at 1 month, which diminished to about one fourth of the sites (SLT = 25%, MTD = 5%) by 3 months. Most of the SSRO group (90%) exhibited no residual deficit 6 months following surgery. The IVRO group had few sites with immediate NSD (SLT = 11%, MTD = 15%). In none of the surgical groups was a statistically significant correlation found between the severity of the initial NSD and length of time to complete recovery.
Address corre spondence and reprint reque sts to Dr Boyd: Division of Oral and Maxillofacial Surgery , 2799 W Grand Blvd, Detroit, MI 48202.
.. Resident, Division of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas. t Head , Division of Oral and Maxillofacial Surgery, Henry Ford Hospital, Detroit, MI. :j: Chairman and Professor, Division of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas.
©1990 American Association of Oral and Maxillofacial Surgeons 0278-2391/90 /4802-0003$3.00/0
124
125
KARAS, BOYD, AND SINN
Most osteotomies designed to correct dentoskeletal deformities are performed close to peripheral branches of the maxillary and mandibular divisions of the trigeminal nerve. Several investigators have retrospectively studied the incidence and severity of neurosensory deficits following orthognathic surgery.l!" and great variability in nerve dysfunction has been reported, even for the same surgical procedure. The reason for this discrepancy is likely to be multifactorial, but a major source of variation is probably attributable to the manner in which neurosensory function was assessed. Early reports studied dysfunction only subjectively by retrospective surveys or questionnaires. In those investigations in which objective testing has been used, studies have differed in the type of sensory function examined (ie, nociception vs. touch discrimination), the sensitivity and specificity of the testing modality, and the postsurgical examination interval. . All procedures studied have the potential for producing alterations in neurosensory function, but it appears that the sagittal split ramus osteotomy (SSRO) used to correct mandibular deformities has the greatest propensity to produce such deficits. Neurosensory dysfunction following SSRO has been documented retrospectively using a variety of subjective and objective testing modalities which vary significantly in their ability to detect specific deficits and to quantify the severity of such deficits. 1.3-12 Most investigators have used skin scratching or cotton wool as a stimulus for light touch perception, which provides only a gross measure of sensation. Recent investigators1,3.4,6,10 have used techniques such as calibrated nylon filaments (von Frey hairs) which allow for a more precise quantification of the deficit. This quantification factor is very important because it allows objective documentation of improvement (or degradation) in function over time. The major weakness of previous studies is that they were retrospective and the postsurgical examination intervals were not standardized. By not documenting sensation before surgery a comparison must be made to published normal values or other unaffected anatomic sites of the face, instead of using each patient as his own control. The remainder of the commonly performed surgical procedures have been studied much less than the SSRO. Several studies indicate that the intraoral vertical ramus osteotomy (IVRO) used to correct mandibular prognathia is associated with considerably less long-term neurosensory deficit than the SSRO.6.14-17 However, there is still a wide spectrum of variability reported, ranging from com-
plete absence of neurosensory deficits'? to deficits in 54% of patients. 10 Neurosensory dysfunction following isolated genioplasty procedures has also been reported and appears to be less prevalent than that reported for the SSRO. 1.2 Neurosensory alterations following maxillary surgery have not been extensively studied, with the few reports available focusing on changes in tooth vitality and intraoral sensation.Pv'? No studies have comprehensively evaluated changes in cutaneous sensation following Le Fort I osteotomy (LEFORT). Although considerable knowledge has been gained from these retrospective studies about longterm neurosensory alterations, there is still an incomplete understanding of the pattern of recovery of neurosensory function following specific orthognathic surgical procedures. The aim of this investigation was to prospectively define the recovery patterns of touch perception using three common neurosensory tests following LEFORT, SSRO, IVRO, and genioplasty (GENIO). Because each surgical procedure differs in its proximity to peripheral branches of the trigeminal nerve, it was hypothesized that each procedure would vary in its propensity to produce alterations in sensory function. Materials and Methods PATIENT PROFILE AND SURGICAL TECHNIQUE
The study group in this investigation consisted of 22 consecutively treated white patients, 16 females and 6 males, who presented to the University of Texas Southwestern Medical Center at Dallas for surgical correction of dentofacial deformity. The mean age of the group was 27 years, with a range of 16 to 50. A total of 40 surgical procedures were performed on the study group. The group was subdivided into four subgroups based on surgical procedure, which included LEFORT (n = 13), SSRO (n = 6), IVRO (n = 9), and GENIO (n = 5). This represented 16 cases of isolated maxillary (7) or mandibular (9) procedures, and 6 cases of simultaneous maxillary and mandibular surgery. All procedures were performed by one of two investigators (S.B.B., D.P.S.) using standard methods to accomplish the osteotomies.i'' Bone plates and screws were used for stabilization of the LEFORT and SSRO. Anterior bone plates at the piriform rim and posterior zygomatic suspension wires were used to stabilize the maxilla. Three 2-mm noncompression (positional) bicortical screws were placed along the superior border of each ramus via an intraoral route to stabilize the mandible following SSRO. No max-
126
RECOVERY OF NEUROSENSORY FUNCTION
iIIomandibular fixation was used in the SSRO or LEFORT groups, whereas dental fixation was the sole method of stabilization for the IVRO group. Genioplasty procedures were performed in conjunction with five of the isolated Le Fort I osteotomies, as well as in 83% (517) of the SSRO group and 33% (3/9) of the IVRO patients. None of the patients had previous maxillofacial surgery, or had a neurosensory deficit before surgery. During surgery no cases of severe compression, stretch, or transection of the trigeminal nerve were observed. A standardized regimen of perioperative corticosteroid therapy was used in each patient which consisted of intravenous methylprednisolone sodium succinate (125 mg) 30 minutes before the surgery with repeat doses every 4 hours for a total of 36 hours. This was followed by a single tapering dose of intramuscular corticosteroid (methylprednisolone acetate 80 mg). NEUROSENSORY TESTING
Cutaneous touch-pressure sensation was evaluated by testing for static light touch, moving touch discrimination, and two-point discrimination. The data were collected independent of assessment by the treating clinician, by one investigator (N.D.K.) using a standard technique of neurosensory evaluation. Patients were evaluated preoperatively (within I week of surgery), and at 3 days, I week, I month, 3 months, and 6 months postoperatively. Seven facial regions were examined corresponding to the peripheral distribution of the maxillary and mandibular branches of the trigeminal nerve, which included the infraorbital, upper lip, and lower lip regions bilaterally, as well as a single chin site. The testing procedures were explained and demonstrated to the patient before each test session. For the purposes of this study, a neurosensory deficit (NSD) was defined as any decrease in touch perception from presurgical levels for a given test. For each surgical group, deficits were expressed as a percentage of anatomic sites involved. Static light touch (SLT) thresholds for each anatomic site were measured using the SemmesWeinstein pressure aesthesiometer (Research Designs, Inc, Houston, TX), which consists of20 nylon monofilaments mounted in Lucite rods labeled 1.65 to 6.65. Each designation represents the logarithm of 10 times the force in milligrams required to bow the monofilament." The testing apparatus is actually a modification of the system originally introduced by von Frey in 1898 which used horsehairs of varying thickness as a stimulus. The testing protocol used in this study was a modification of that described by Orner." Starting with the least-stiff filament (1.65), the stimulus was applied three times
to a designated test site while the patient's eyes were closed. The very light filaments (1.65 to 3.84) were "bounced off' the skin for adequate stimulation and were applied in series until the patient felt a minimum two out of three applications. The heavier filaments (4.08 and 6.65) were applied only once, and the filament size was increased until a positive response was elicited. Moving light touch discrimination (MLT) was measured by stimulation with a No. 2 sable-hair brush. Each anatomic site was stimulated by a brush stroke applied in a direction selected at random (either horizontal or vertical) while the patient's eyes were closed. Three brush strokes constituted a trial, and a series of three trials were performed at each site. Two-point discrimination (TPD) was tested using a Boley gauge with the points of the gauge blunted so as not to elicit a painful response from the patient. The gauge was set at 10 mm separation and applied to the skin with equal pressure on each point in a manner intended to stimulate but not blanch the skin. The two-point stimulus was applied three times at each setting, and the distance was changed until the patient could no longer discriminate two pcints.I! All data were entered into a microcomputer database (dBase III +, Ashton-Tate, Inc, Torrance, CAl and statistical analysis was completed using SAS statistical software (SAS Institute, Inc, Cary, NC). For each surgical group descriptive statistical methods were used to determine the percentage of anatomic sites with deficits, the severity of the deficits, and recovery over time. Between-group comparisons were done with repeated-measures ANOVA methods. Subsequent within-group comparisons were performed via Bonferroni adjusted paired t tests comparing each postsurgical time period with preoperative values. Spearman's rho correlation-regression analysis was used to determine if a significant relationship existed between the severity of the initial deficit and length of time to complete recovery. Throughout this investigation, P < .05 was considered to represent a statistically significant difference. Results LE FORT
I OSTEOTOMY
Static Light Touch Preoperatively all patients in the group responded to the finest filament (1.65) for the infraorbital and upper lip sites. Immediately following surgery, deficits were observed in 58% of the infraorbital and 40% of the upper lip regions (Fig IA). On average, this represented a decrease in sensitivity by three and two filaments in the infraorbital and upper lip
127
KARAS, BOYD, AND SINN loo~------------------------'"
(0)
0 - 0 INl1W>R!lTAL .... - .... UPPERUP
so 80
70 60 SO 40 30 20 10
LEFORT
o -10 +-....-..-,.--,r--
Recovery of Neurosensory Function Following Orthognathic Surgery NESTOR D. KARAS, DDS,· SCOTT B. BOYD, DDS, PHD,t AND DOUGLAS P. SINN, DOS:f:
The purpose of this study was to prospectively define the recovery of touch discrimination following four commonly performed surgical procedures in 22 consecutive patients with no previous maxillofacial surgery. The surgical groups studied were Le Fort I osteotomy (LEFORT; n = 13), sagittal split ramus osteotomy (SSRO; n = 6), intraoral vertical ramus osteotomy (IVRO; n = 9), and isolated genioplasty (GENIO; n = 5). Neurosensory function was assessed by three different testing modalities which included static light touch (SLT), moving touch discrimination (MTD), and two-point discrimination (TPD). Cutaneous sensation of the lower lip and chin were examined for the mandibular procedures, whereas the infraorbital and upper lip regions were evaluated following maxillary surgery. Immediately following surgery, each group varied in both the incidence and magnitude of neurosensory deficits (NSD). The SSRO group had the highest percentage of sites with immediate postsurgical NSD to both SLT (72%) and MTD (67%), followed by the LEFORT (SLT = 50%, MTD = 58%), GENIO (SLT = 27%, MTD = 6%), and IVRO groups (SLT = 11%, MTD = 18%), respectively . Each group also varied in the severity of the initial postoperative deficit as measured by SLT, with the SSRO group showing the greatest deficit followed by the LEFORT, GENIO, and IVRO groups. During the 6-month recovery period each group approached preoperative levels of sensation at a different rate. The LEFORT group recovered most rapidly, with few anatomic sites showing NSD (SLT = 20%, MTD = 5%) at the 1-month postoperative examination, and the majority of the group (96%) returned to preoperative sensation by 3 months following surgery. The SSRO group recovered more slowly, with approximately half of the group demonstrating a deficit (SLT = 50%, MTD = 59%) at 1 month, which diminished to about one fourth of the sites (SLT = 25%, MTD = 5%) by 3 months. Most of the SSRO group (90%) exhibited no residual deficit 6 months following surgery. The IVRO group had few sites with immediate NSD (SLT = 11%, MTD = 15%). In none of the surgical groups was a statistically significant correlation found between the severity of the initial NSD and length of time to complete recovery.
Address corre spondence and reprint reque sts to Dr Boyd: Division of Oral and Maxillofacial Surgery , 2799 W Grand Blvd, Detroit, MI 48202.
.. Resident, Division of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas. t Head , Division of Oral and Maxillofacial Surgery, Henry Ford Hospital, Detroit, MI. :j: Chairman and Professor, Division of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas.
©1990 American Association of Oral and Maxillofacial Surgeons 0278-2391/90 /4802-0003$3.00/0
124
125
KARAS, BOYD, AND SINN
Most osteotomies designed to correct dentoskeletal deformities are performed close to peripheral branches of the maxillary and mandibular divisions of the trigeminal nerve. Several investigators have retrospectively studied the incidence and severity of neurosensory deficits following orthognathic surgery.l!" and great variability in nerve dysfunction has been reported, even for the same surgical procedure. The reason for this discrepancy is likely to be multifactorial, but a major source of variation is probably attributable to the manner in which neurosensory function was assessed. Early reports studied dysfunction only subjectively by retrospective surveys or questionnaires. In those investigations in which objective testing has been used, studies have differed in the type of sensory function examined (ie, nociception vs. touch discrimination), the sensitivity and specificity of the testing modality, and the postsurgical examination interval. . All procedures studied have the potential for producing alterations in neurosensory function, but it appears that the sagittal split ramus osteotomy (SSRO) used to correct mandibular deformities has the greatest propensity to produce such deficits. Neurosensory dysfunction following SSRO has been documented retrospectively using a variety of subjective and objective testing modalities which vary significantly in their ability to detect specific deficits and to quantify the severity of such deficits. 1.3-12 Most investigators have used skin scratching or cotton wool as a stimulus for light touch perception, which provides only a gross measure of sensation. Recent investigators1,3.4,6,10 have used techniques such as calibrated nylon filaments (von Frey hairs) which allow for a more precise quantification of the deficit. This quantification factor is very important because it allows objective documentation of improvement (or degradation) in function over time. The major weakness of previous studies is that they were retrospective and the postsurgical examination intervals were not standardized. By not documenting sensation before surgery a comparison must be made to published normal values or other unaffected anatomic sites of the face, instead of using each patient as his own control. The remainder of the commonly performed surgical procedures have been studied much less than the SSRO. Several studies indicate that the intraoral vertical ramus osteotomy (IVRO) used to correct mandibular prognathia is associated with considerably less long-term neurosensory deficit than the SSRO.6.14-17 However, there is still a wide spectrum of variability reported, ranging from com-
plete absence of neurosensory deficits'? to deficits in 54% of patients. 10 Neurosensory dysfunction following isolated genioplasty procedures has also been reported and appears to be less prevalent than that reported for the SSRO. 1.2 Neurosensory alterations following maxillary surgery have not been extensively studied, with the few reports available focusing on changes in tooth vitality and intraoral sensation.Pv'? No studies have comprehensively evaluated changes in cutaneous sensation following Le Fort I osteotomy (LEFORT). Although considerable knowledge has been gained from these retrospective studies about longterm neurosensory alterations, there is still an incomplete understanding of the pattern of recovery of neurosensory function following specific orthognathic surgical procedures. The aim of this investigation was to prospectively define the recovery patterns of touch perception using three common neurosensory tests following LEFORT, SSRO, IVRO, and genioplasty (GENIO). Because each surgical procedure differs in its proximity to peripheral branches of the trigeminal nerve, it was hypothesized that each procedure would vary in its propensity to produce alterations in sensory function. Materials and Methods PATIENT PROFILE AND SURGICAL TECHNIQUE
The study group in this investigation consisted of 22 consecutively treated white patients, 16 females and 6 males, who presented to the University of Texas Southwestern Medical Center at Dallas for surgical correction of dentofacial deformity. The mean age of the group was 27 years, with a range of 16 to 50. A total of 40 surgical procedures were performed on the study group. The group was subdivided into four subgroups based on surgical procedure, which included LEFORT (n = 13), SSRO (n = 6), IVRO (n = 9), and GENIO (n = 5). This represented 16 cases of isolated maxillary (7) or mandibular (9) procedures, and 6 cases of simultaneous maxillary and mandibular surgery. All procedures were performed by one of two investigators (S.B.B., D.P.S.) using standard methods to accomplish the osteotomies.i'' Bone plates and screws were used for stabilization of the LEFORT and SSRO. Anterior bone plates at the piriform rim and posterior zygomatic suspension wires were used to stabilize the maxilla. Three 2-mm noncompression (positional) bicortical screws were placed along the superior border of each ramus via an intraoral route to stabilize the mandible following SSRO. No max-
126
RECOVERY OF NEUROSENSORY FUNCTION
iIIomandibular fixation was used in the SSRO or LEFORT groups, whereas dental fixation was the sole method of stabilization for the IVRO group. Genioplasty procedures were performed in conjunction with five of the isolated Le Fort I osteotomies, as well as in 83% (517) of the SSRO group and 33% (3/9) of the IVRO patients. None of the patients had previous maxillofacial surgery, or had a neurosensory deficit before surgery. During surgery no cases of severe compression, stretch, or transection of the trigeminal nerve were observed. A standardized regimen of perioperative corticosteroid therapy was used in each patient which consisted of intravenous methylprednisolone sodium succinate (125 mg) 30 minutes before the surgery with repeat doses every 4 hours for a total of 36 hours. This was followed by a single tapering dose of intramuscular corticosteroid (methylprednisolone acetate 80 mg). NEUROSENSORY TESTING
Cutaneous touch-pressure sensation was evaluated by testing for static light touch, moving touch discrimination, and two-point discrimination. The data were collected independent of assessment by the treating clinician, by one investigator (N.D.K.) using a standard technique of neurosensory evaluation. Patients were evaluated preoperatively (within I week of surgery), and at 3 days, I week, I month, 3 months, and 6 months postoperatively. Seven facial regions were examined corresponding to the peripheral distribution of the maxillary and mandibular branches of the trigeminal nerve, which included the infraorbital, upper lip, and lower lip regions bilaterally, as well as a single chin site. The testing procedures were explained and demonstrated to the patient before each test session. For the purposes of this study, a neurosensory deficit (NSD) was defined as any decrease in touch perception from presurgical levels for a given test. For each surgical group, deficits were expressed as a percentage of anatomic sites involved. Static light touch (SLT) thresholds for each anatomic site were measured using the SemmesWeinstein pressure aesthesiometer (Research Designs, Inc, Houston, TX), which consists of20 nylon monofilaments mounted in Lucite rods labeled 1.65 to 6.65. Each designation represents the logarithm of 10 times the force in milligrams required to bow the monofilament." The testing apparatus is actually a modification of the system originally introduced by von Frey in 1898 which used horsehairs of varying thickness as a stimulus. The testing protocol used in this study was a modification of that described by Orner." Starting with the least-stiff filament (1.65), the stimulus was applied three times
to a designated test site while the patient's eyes were closed. The very light filaments (1.65 to 3.84) were "bounced off' the skin for adequate stimulation and were applied in series until the patient felt a minimum two out of three applications. The heavier filaments (4.08 and 6.65) were applied only once, and the filament size was increased until a positive response was elicited. Moving light touch discrimination (MLT) was measured by stimulation with a No. 2 sable-hair brush. Each anatomic site was stimulated by a brush stroke applied in a direction selected at random (either horizontal or vertical) while the patient's eyes were closed. Three brush strokes constituted a trial, and a series of three trials were performed at each site. Two-point discrimination (TPD) was tested using a Boley gauge with the points of the gauge blunted so as not to elicit a painful response from the patient. The gauge was set at 10 mm separation and applied to the skin with equal pressure on each point in a manner intended to stimulate but not blanch the skin. The two-point stimulus was applied three times at each setting, and the distance was changed until the patient could no longer discriminate two pcints.I! All data were entered into a microcomputer database (dBase III +, Ashton-Tate, Inc, Torrance, CAl and statistical analysis was completed using SAS statistical software (SAS Institute, Inc, Cary, NC). For each surgical group descriptive statistical methods were used to determine the percentage of anatomic sites with deficits, the severity of the deficits, and recovery over time. Between-group comparisons were done with repeated-measures ANOVA methods. Subsequent within-group comparisons were performed via Bonferroni adjusted paired t tests comparing each postsurgical time period with preoperative values. Spearman's rho correlation-regression analysis was used to determine if a significant relationship existed between the severity of the initial deficit and length of time to complete recovery. Throughout this investigation, P < .05 was considered to represent a statistically significant difference. Results LE FORT
I OSTEOTOMY
Static Light Touch Preoperatively all patients in the group responded to the finest filament (1.65) for the infraorbital and upper lip sites. Immediately following surgery, deficits were observed in 58% of the infraorbital and 40% of the upper lip regions (Fig IA). On average, this represented a decrease in sensitivity by three and two filaments in the infraorbital and upper lip
127
KARAS, BOYD, AND SINN loo~------------------------'"
(0)
0 - 0 INl1W>R!lTAL .... - .... UPPERUP
so 80
70 60 SO 40 30 20 10
LEFORT
o -10 +-....-..-,.--,r--
