Keywords obese - pain - trigeminal neuralgia - microvascular decompression - surgical complications
- reoperation
Introduction
Microvascular decompression (MVD) is considered an excellent treatment for medically
refractory trigeminal neuralgia (TN) and hemifacial spasm (HFS).[1 ]
[2 ] TN and HFS are thought to occur due to arterial or venous compression of associated
cranial nerves at the nerve root entry zone on the brain stem.[3 ] The most common offending vessel in TN is either the superior cerebellar artery
or the anterior inferior cerebellar artery (AICA), whereas in HFS the AICA or the
posterior inferior cerebellar artery commonly compress the cranial nerve.[4 ]
[5 ]
MVD provides excellent long-lasting results for both TN and HFS.[5 ]
[6 ] Compared with percutaneous interventions for TN such as glycerol or radiofrequency
rhizotomy, and balloon compression, MVD provides both a higher rate of long-term patient
satisfaction and a lower rate of pain recurrence.[7 ] MVD has been reported with an initial success rate of 80 to 95%, and 70% of patients
are pain-free and off medications at 10 years' postsurgery.[8 ]
[9 ]
[10 ] Radiosurgery is also a well-established and safe alternative for primary or refractory
treatment of TN demonstrating high response rates for treatment.[11 ] Unlike other invasive interventions, however, patients treated with radiosurgery
often have persistent or recurrent pain requiring additional procedures.
Among the available interventions to treat TN or HFS, MVD is undeniably the most invasive
as it requires intracranial access via a burr hole or small craniotomy followed by
surgical navigation around and manipulation of delicate neurovascular structures on
the brainstem.[12 ] Postoperative complications following MVD are generally low, reported as less than
10% and can include cranial nerve palsy, cerebrospinal fluid (CSF) leak, infection,
stroke, and in rare cases, hemorrhage, or death.[8 ]
[9 ]
[13 ]
[14 ]
[15 ] Risk factors associated with increased likelihood of postoperative complications
include high body mass index (BMI), American Society of Anesthesiologists (ASA) class
II to III, hypertension, tobacco use, chronic obstructive pulmonary disease (COPD),
diabetes, and increased procedure duration.[13 ]
[16 ]
[17 ]
[18 ]
Surprisingly, reoperation rates have been reported as high as 11% and most commonly
occur due to wound infection, wound dehiscence, CSF leak, or refractory/recurrent
pain.[6 ]
[13 ]
[17 ]
[19 ] Risk factors for reoperation have been linked to obesity and diabetes but in series
with small sample sizes.[17 ] Given the relatively high and unacceptable rate of reoperation for an elective procedure
with reasonable treatment alternatives, we sought to further elucidate and characterize
these risk factors for reoperation for MVD with the goal of potentially identifying
a patient population that may benefit from further optimization prior to surgery and/or
alternative initial treatment options. We hypothesized that morbidly obese (BMI ≥
40) patients are at greater risk for reoperation following MVD.
Methods
Data Source
Patient data from 2015 to 2020 were obtained from the American College of Surgeons–National
Surgical Quality Improvement Program (ACS-NSQIP) database. The NSQIP database contains
validated, multi-institutional data collected by trained surgical reviewers across
institutions using a uniform protocol.[20 ] Details on the sampling strategy, data abstraction procedure, variables, outcomes,
and structure of the NSQIP have been previously published.[21 ]
[22 ]
[23 ] Trained reviewers at individual hospitals prospectively collect patient data on
more than 200 variables including patient demographics, comorbid conditions, operative
details, and 30-day postoperative outcomes. Data audits are regularly performed to
ensure data reliability. This study was exempt from the institutional review board
(IRB) approval as only deidentified data were received and analyzed.
Patient Population
Patients were included in this study if they had a diagnosis of TN or HFS for which
they underwent a procedure with a current procedural terminology (CPT) code 61458,
corresponding to a suboccipital craniotomy for exploration or decompression of cranial
nerves. All procedures were performed under general anesthesia and patients were older
than or equal to 18 years of age. Patient demographics and comorbidities were collected
from the NSQIP database and include age, gender, BMI, hypertension, diabetes, smoking
history, COPD, dyspnea, steroid use, bleeding disorder, recent weight loss, and ASA
Classification System I, II, and ≥III. BMI was categorized into <30, 30–34.9, 35–39.9,
and ≥40. Preoperative labs were collected and include platelets, partial thromboplastin
time, and international normalized ratio. Procedure duration was defined as minutes
from procedure start to finish (from skin incision to skin closure).
Reoperation was defined as any patient with an MVD that returned to the operating
room within 30 days related to the original surgery. CPT codes were provided for the
reasons of unplanned reoperation and grouped together based on similarity. Reasons
for reoperation included CSF leak (CPT codes 62100, 61618, 63709, 63707), wound complications
(CPT codes 13160, 10180, 10120, 11042), refractory pain (CPT codes 61458, 64610),
and intracranial hemorrhage (CPT codes 61315). Several CPT codes were placed in an
other/unknown category (CPT 62142, 61304, 61345, 62146, 62160) because the CPT description
was ambiguous or not provided. Frequency of 30-day postoperative complications were
determined for the cohort and included superficial and deep wound infection, wound
dehiscence, pneumonia, reintubation, deep vein thrombosis, pulmonary embolism, failure
to wean, urinary tract infection, stroke, cardiac arrest, myocardial infarction, sepsis,
readmission, and reoperation.
Statistical Analysis
Statistical analysis was performed using JMP Pro (Version 17.0.0, 2021 SAS Institute
Inc.). Based on previous literature and our hypothesis, patient demographics, comorbidities,
and outcomes were compared with the patient sample grouped into BMI < 40 and ≥40.
Descriptive analyses were obtained, and the incidence of 30-day postoperative complications
were determined for the entire sample size and patients based on BMI. Differences
between normally and non-normally distributed continuous variables were compared using
Welch's t -tests and Wilcoxon rank-sum tests, respectively. Fisher's exact tests were used to
evaluate categorical variables. Logistic regression analysis was used to model the
association of risk factors with reoperation. A univariate analysis was first performed
and any factor with a p ≤ 0.15 was included in the multivariate analysis for reoperation. A multivariate
logistic regression analysis was also performed including diabetes and BMI variables
on the indication for reoperation for the two most common indications for reoperation.
Statistical significance was defined as p < 0.05; all statistical tests were two-sided.
Results
Patient Characteristics and Indications for Reoperation
A total of 1,303 patients met the criteria for this study. Demographics, comorbidities,
and clinical characteristics are provided in [Table 1 ]. The average age of the cohort was 56.9 (standard deviation [SD] = 13.4) and predominantly
female (68.6%). A little more than half of the patients were normal weight with a
BMI < 30 (58.8%). The most common medical comorbidities included hypertension (37.8%)
and diabetes (8.6%), and 14.6% of the cohort smoked tobacco. ASA class was grouped
into class I (4.2%), II (57.5%), and ≥III (38.2%). Forty-two patients (3.2%) returned
to the operating room within 30 days postoperatively ([Table 1 ]). The most common indications for reoperation were CSF leak (31%), followed by wound
complications including infections and wound breakdown (19%).
Table 1
Patient characteristics, comorbidities, and postoperative outcomes
Patient characteristics
All
BMI < 40
BMI ≥ 40
p -Value
N
1,303
1,211
92
Age
56.9 (13.4)
57.4 (13.4)
50.1 (12.1)
<0.0001[a ]
Gender
Male
409 (31.4)
383 (31.7)
26 (28.3)
Female
894 (68.6)
827 (68.3)
66 (71.7)
0.56
BMI
< 30
766 (58.8)
–
–
–
30–34.9
285 (21.9)
–
–
–
35–39.9
159 (12.2)
–
–
–
≥40
92 (7.1)
–
–
–
Comorbidities
HTN
493 (37.8)
437 (33.6)
56 (60.9)
<0.0001[a ]
Diabetes
112 (8.6)
94 (7.7)
15 (16.3)
0.0002[a ]
Smoking history
190 (14.6)
181 (15.0)
9 (9.8)
0.22
COPD
11 (0.84)
10 (0.83)
1 (1.1)
0.55
CHF
0 (0.0)
0 (0.0)
0 (0.0)
−
Dyspnea
32 (2.5)
31 (2.6)
1 (1.1)
0.76
Steroid use
30 (2.3)
27 (2.2)
3 (3.3)
0.46
Bleeding disorder
11 (0.84)
7 (0.58)
4 (4.3)
0.0001[a ]
Recent weight loss
7 (0.54)
7 (0.58)
0 (0.0)
1.0
ASA class
I
55 (4.2)
53 (4.4)
2 (2.2)
II
749 (57.5)
723 (59.8)
26 (28.3)
≥III
498 (38.2)
434 (35.8)
64 (69.6)
<0.0001[a ]
Preoperative labs
Platelets
242 (72.4)
243 (10.8)
0.95
PTT
29.1 (4.2)
31 (8.9)
0.12
INR
0.99
1.03
0.15
Procedure duration (min)
164.8 (58.0)
163.8 (57.5)
178.7 (60.2)
0.02[a ]
Hospital LOS (d)
2.8 (3.5)
2.7 (3.6)
3.0 (2.54)
0.31
30-day postoperative complications
72 (5.5)
65 (5.4)
7 (7.6)
0.37
Superficial wound infection
14 (1.1)
12 (0.99)
2 (2.2)
0.45
Deep wound infection
4 (0.31)
3 (0.25)
1 (1.1)
0.45
Wound dehiscence
1 (0.08)
1 (0.08)
0 (0.0)
0.78
Pneumonia
5 (0.38)
5 (0.41)
0 (0.0)
0.54
Reintubation
4 (0.31)
2 (0.17)
2 (2.2)
0.19
Deep vein thrombosis
4 (0.31)
4 (0.33)
0 (0.0)
0.58
Pulmonary embolism
2 (0.15)
2 (0.17)
0 (0.0)
0.69
Failure to wean
2 (0.15)
2 (0.17)
0 (0.0)
0.69
Urinary tract infection
17 (1.3)
17 (1.4)
0 (0.0)
0.25
Stroke
8 (0.61)
8 (0.66)
0 (0.0)
0.43
Cardiac arrest
2 (0.15)
2 (0.17)
0 (0.0)
0.69
Myocardial infarction
2 (0.15)
2 (0.17)
0 (0.0)
0.69
Sepsis
10 (0.77)
9 (0.74)
1 (1.1)
0.72
Mortality
1 (0.08)
1 (0.08)
0 (0.0)
0.78
Readmission
76 (5.8)
68 (5.6)
8 (8.7)
0.10
Time to readmission (d)
13.8 (7.1)
13.5 (7.2)
16 (6.2)
0.32
Reoperation
42 (3.22)
34 (2.6)
7 (7.6)
0.006[a ]
Time to reoperation (d)
13.8 (8.2)
13.9 (8.2)
14.3 (9.1)
0.99
Abbreviations: ASA, American Society of Anesthesiologists; BMI, body mass index; CHF,
congestive heart failure; COPD, chronic obstructive pulmonary disease; HTN, hypertension;
INR, international normalized ratio; LOS, length of stay; PTT, partial thromboplastin
time.
Notes: Patient sample grouped by BMI < 40 and BMI ≥ 40. Statistical comparison of
means and frequency for patient characteristics and 30-day postoperative outcome provided
by the p -value.
a Statistical significance.
The cohort was grouped by BMI < 40 and ≥40 for comparison analysis based on our literature
review. Among the groups, there were significant differences in patient age (57.4
vs. 50.1, respectively; p < 0.0001) and comorbidities including hypertension (33.6 vs. 60.9%; p < 0.0001), diabetes (7.7 vs. 16.3%; p = 0.0002), bleeding disorders (0.58 vs. 4.3%; p = 0.0001), and ASA Class ≥ III (35.8 vs. 69.6%; p < 0.0001). There were no significant differences between gender, smoking history,
COPD, dyspnea, steroid use, and recent weight loss.
Postoperative Outcomes
Postoperative outcomes are provided in [Table 1 ]. For the entire patient cohort, the mean procedure duration was 164.8 minutes (SD = 58.0).
There was a statistically significant difference between patients with a BMI < 40
and ≥40 in the mean procedure duration (163.8 vs. 178.7 minutes, respectively; p = 0.02). For the entire cohort, the most frequent 30-day postoperative complications
included superficial wound infection (1.1%), urinary tract infection (1.3%), readmission
(5.8%), and reoperation (3.2%). Mean time to return to the operating room was 13.8
days (SD = 8.2). When grouped by BMI < 40 and ≥40, there was a significant difference
between the frequency of reoperation (2.6 vs. 7.6%, respectively; p = 0.006; [Table 1 ]).
A univariate and multivariate logistic regression analysis was performed to evaluate
the relationship between comorbidities and reoperation ([Table 2 ]). Variables that met statistical significance on univariate analysis included diabetes
(odds ratio [OR] = 3.7, 95% confidence interval [CI] = [1.7–7.7]; p = 0.0006), BMI ≥ 40 (OR = 2.79 [1.2–6.7]; p = 0.022), and procedure duration (OR = 1.01 [1.0–1.01]; p = 0.021). On multivariate analysis, diabetes (OR = 2.7 [1.3–5.8]; p = 0.011), BMI ≥ 40 (OR = 2.5 [1.1–6.0]; p = 0.04), and procedure duration (OR = 1.01 [1.0–1.01]; p = 0.028) maintained statistical significance for reoperation. For patients who had
both diabetes and a BMI ≥ 40, there was a statistically significant cumulative increase
in the odds of reoperation (OR = 4.9 [1.07–22.6]; p = 0.04).
Table 2
Univariate and multivariate logistic regression analysis of patient characteristics
and comorbidities on likelihood of reoperation
Odds ratio of reoperation
Univariate OR [95% CI] (p -value)
Multivariate OR [95% CI] (p -value)
Age
0.99 [0.97–1.0] (0.49)
–
Sex
Male
Ref
–
Female
1.11 [0.56–2.19] (0.77)
–
Diabetes
3.66 [1.7–7.7] (0.0006)
2.7 [1.3–5.8] (0.011)
BMI
≤30
Ref
Ref
31–34.9
0.97 [0.43–2.2] (0.96)
1.7 [0.55–2.5] (0.68)
35–39.9
0.87 [0.29–2.6] (0.79)
0.89 [0.33–2.4] (0.82)
≥ 40
2.79 [1.2–6.7] (0.022)
2.5 [1.06–6.0] (0.036)
Diabetes and BMI ≥ 40
–
4.9 [1.07–22.6] (0.04)
Smoking history
1.4 [0.65–3.2] (0.37)
–
Dyspnea
1.1 [0.14–7.9] (0.95)
–
COPD
3.1 [0.39–25.0] (0.28)
–
Hypertension
0.94 [0.49–1.8] (0.87)
–
Steroid use
2.2 [0.52–9.8] (0.28)
–
Bleeding disorder
3.13 [0.39–25.0] (0.28)
–
ASA classification
1
Ref
–
2
0.54 [0.16–1.9] (0.34)
–
3+
0.50 [0.14–1.8] (0.29)
–
Procedure duration
1.01 [1.00–1.01] (0.021)
1.01 [1.00–1.01] (0.028)
Abbreviations: ASA, American Society of Anesthesiologists; BMI, body mass index; CI,
confidence interval; COPD, chronic obstructive pulmonary disorder; OR, odds ratio;
Ref, reference.
Bolded values have p -value significance of <0.05.
In patients with a BMI ≥ 40 and diabetes, there is a near-linear increase in the probability
of reoperation with increasing operation time ([Fig. 1 ]). At the mean procedure length for the cohort with a BMI ≥ 40, the probability of
reoperation is 18%. The projected probability of reoperation increases to 30% for
a procedure duration of 411 minutes in this model.
Fig. 1 Probability of reoperation based on procedure duration. Probability is based on patients
with a BMI ≥ 40 and diabetes. There is a near-linear relationship between procedure
duration and probability of reoperation. (A) At the mean procedure duration for the
with a BMI ≥ 40 (179 minutes), the probability of reoperation is 18%. (B) At the longest
procedure duration that is calculated by the model (411 minutes), the risk of reoperation
increases to 30%.
The indications for reoperation included CSF leak (n = 31, 31% of reoperations), wound complications (n = 8, 19% of reoperations), refractory pain (n = 5, 11.9% of reoperations), intracranial hemorrhage (n = 2, 4.8% of reoperations), and other (n = 14, 33.3% of reoperations; [Table 3 ]). A multivariate logistic regression analysis was performed to determine the association
of diabetes and BMI by specific indication for reoperation ([Table 4 ]). The sample sizes allowed for analysis for CSF leak and wound breakdown only. For
wound complications, we found significance with diabetes (OR = 8.3 [1.9–35.5]; p = 0.005) and BMI ≥ 40 (OR = 8.2 [1.4–57.8]; p = 0.0226). Additionally, there was an increased risk of CSF leak with increasing
procedure duration (OR = 1.01 [1.00–1.02]; p = 0.0089). Diabetes and BMI were not associated with CSF leak.
Table 3
Indication for reoperation with corresponding CPT code, procedure detail, and total
number of patients with percent frequency in the entire sample and within the reoperations
group
Indication
CPT
Procedure
N , %
% of reoperations
CSF leak
13 (1.0)
31.0
62100
Craniotomy for repair of dural/cerebrospinal fluid leak
7 (0.54)
16.7
61618
Secondary repair of dura for cerebrospinal fluid leak, anterior, middle or posterior
cranial fossa following surgery of the skull base; by free tissue graft
3 (0.23)
7.1
63709
Repair of dural/cerebrospinal fluid leak or pseudomeningocele, with laminectomy
1 (0.08)
2.4
63707
Repair of dural/cerebrospinal fluid leak, not requiring laminectomy
2 (0.15)
4.8
Wound complications
8 (0.61)
19.0
13160
Secondary closure of surgical wound or dehiscence, extensive or complicated
4 (0.31)
9.5
10180
Incision and drainage, complex, postoperative wound infection
2 (0.15)
4.7
10120
Incision and removal of foreign body, subcutaneous tissues; simple
1 (0.08)
2.4
11042
Debridement, subcutaneous tissue
1 (0.08)
2.4
Refractory pain
5 (0.38)
11.9
61458
Craniectomy, suboccipital; for exploration or decompression of cranial nerves
3 (0.23)
7.1
64610
Destruction by neurolytic agent, trigeminal nerve; supraorbital, infraorbital, mental,
or inferior alveolar branch; second and third division branches at foramen ovale under
radiologic monitoring
2 (0.15)
4.8
Intracranial hemorrhage
2 (0.15)
4.8
61315
Craniectomy or craniotomy for evacuation of hematoma, infratentorial; extradural or
subdural; intracerebral
2 (0.15)
4.8
Other/unknown
14
33.3
62142
Removal of bone flap or prosthetic plate of skull
2 (0.15)
4.78
61304
Craniectomy or craniotomy, exploratory; supratentorial
1 (0.08)
2.4
61345
Other cranial decompression, posterior fossa
1 (0.08)
2.4
62146
Cranioplasty with autograft
1 (0.08)
2.4
62160
Neuroendoscopy, intracranial, for placement or replacement of ventricular catheter
and attachment to shunt system or external drainage
1 (0.08)
2.4
61321
Incision and subcutaneous placement of cranial bone graft; infratentorial
1 (0.08)
2.4
NA
Not reported
7 (0.54)
16.7
Total
42
Abbreviations: CPT, current procedural terminology; CSF, cerebrospinal fluid; NA,
not applicable.
Table 4
Multivariate logistic regression analysis of risk factors for cerebrospinal fluid
leak and wound complications leading to reoperation
Multivariate odds ratio of complications
CSF leak
(n = 13)
Wound complications
(n = 8)
Diabetes
2.16 [0.45–10.3] (0.33)
8.3 [1.9–35.5] (0.005)
BMI
≤30
Ref
Ref
31–34.9
0.94 [0.24–3.62] (0.93)
1.97 [0.11–16.7] (0.51)
35–39.9
NA
1.42 [0.12–16.7] (0.78)
≥40
1.8 [0.36–8.99] (0.47)
8.2 [1.4–57.8] (0.0226)
Procedure time
1.01 [1.00–1.02] (0.0089)
0.99 [0.98–1.01] (0.36)
Abbreviations: BMI, body mass index; CPT, current procedural terminology; CSF, cerebrospinal
fluid; NA, not applicable; Ref, reference.
Bolded values have p -value significance of <0.05.
Discussion
Reoperation after an MVD has been reported as high as 11%[10 ] and typically occurs due to CSF leak, surgical site infection, or recurrent/persistent
pain or spasm.[17 ] The reoperation rate is unacceptably high for a surgery with reasonable alternative
treatment options. Moreover, postoperative complications following repeat surgery
has been reported at 37% and includes facial numbness, hearing loss, infection, and
CSF leak.[15 ] The high rates of reoperation surgery and associated complications emphasize the
importance of identifying these high-risk patient populations for preoperative optimization
or alternative treatment strategies.
We demonstrate that 30-day postoperative reoperation rate is associated with morbid
obesity (BMI ≥ 40), diabetes, and increasing procedure duration. Most common indications
for reoperation included CSF leak, wound-related issues (dehiscence and/or infection),
and refractory symptoms. Using this larger sample size, we found that a patient with
either diabetes or BMI ≥ 40 is associated with a 2-fold increase in risk of reoperation,
while having both diabetes and BMI ≥ 40 has an almost 5 times the risk of reoperation.
In addition, we show a linear-type relationship in the probability of reoperation
and procedure duration for patients with a BMI ≥ 40 and diabetes such that the risk
of reoperation for the mean procedure duration is 18% and, with increasing procedure
duration, increases to as high as 30%. Given that patients with a BMI ≥ 40 consist
of 7% of the population receiving an MVD, these are important findings that can impact
a significant portion a neurosurgeon's patient population and potential management.
Patients with diabetes and/or morbid obesity are in a chronic state of inflammation
and dysmetabolism, impeding wound healing and increasing the risk of infection.[24 ]
[25 ]
[26 ]
[27 ]
[28 ]
[29 ] Obesity also increases tension on the fascial edges of the wound closure, directly
contributing to wound dehiscence.[29 ] Indeed, patients with BMI ≥ 40 had rates of reoperation of 8% compared with 3% in
patients with BMI < 40 in this study. Our findings are consistent with and support
a prior NSQIP study from 2017 by Arnone et al that investigated risk factors associated
with readmission and reoperation. This study demonstrated that patients with morbid
obesity (9.5%; OR = 5.3; p = 0.030) and diabetes (11.8%; OR = 6.32; p = 0.017) have increased risk of reoperation after an MVD.[17 ] Although this study was the first to demonstrate this relationship, its findings
were limited and restrictive because there were only 14 cases of reoperation. With
a larger sample size and 42 cases of reoperation, we were able to conduct univariate
and multivariate logistic regression analysis on the risk factors and indications
for reoperation, which have not been previously published.
Patients with morbid obesity had a statistically significant longer surgical time.
It is possible an increase in procedure duration reflects the increased challenges
with exposing the relatively small corridor used for MVD associated with a larger
body habitus. The difficulties leading to an increase in procedure duration, such
as difficult exposure and/or closure with a more limited access. Whereas morbid obesity
and diabetes were not correlated with CSF leak, longer procedure time was independently
associated with increased risk of CSF leak ([Table 4 ]). We hypothesize that, unlike wound complications, where patients with morbid obesity
may have wound healing issues due to poor skin integrity related to medical and nutritional
confounders, CSF leaks may be more likely due to incomplete closure of dura or opening
of the mastoid air cells that cannot be adequately repaired due to body habitus and
exposure. These factors do not appear to be influenced by BMI, but rather procedure
length may reflect possible challenges due to morbid obesity encountered intraoperatively
that may increase the risk of CSF leak.
Interestingly, we found that for every increasing minute of procedure duration, there
is a 1% increased risk of reoperation ([Table 2 ]). This is particularly applicable for patients with higher BMIs who have an on average
longer procedure duration. Indeed, we demonstrate the near-linear relationship of
procedure duration and the predicted risk of reoperation in patients with diabetes
and a BMI ≥ 40. At the mean procedure duration (164 minutes), the predicted probability
of reoperation is 18%. The highest predicted probability for a procedure duration
of approximately 400 minutes is as high as 30%. Importantly, the procedure duration,
recorded as time from skin opening to closure in the NSQIP database, underestimates
the overall time the patient is in the operating room and at risk for perioperative
complications. The critical periods between anesthesia induction and waking are especially
tenuous for patients with obesity who are at increased risk of perioperative respiratory
failure, aspiration, myocardial infarction, infection, and anesthetic failure.[28 ]
[30 ]
Alternative treatment strategies may be considered for patients with morbid obesity
and/or diabetes. Stereotactic radiosurgery (SRS) is a recognized alternative and effective
means for providing relief for patients with TN.[31 ]
[32 ] Interestingly, in a retrospective study, Khattab et al found that patients with
a BMI > 25 had a poorer response and lesser improvement to pain post-SRS, perhaps
due to a blunted response to SRS therapy.[16 ] Although Botox injections are routinely used for HFS, the mean duration of effect
is typically 12 weeks, requiring repeat injections for continued relief. Medical therapy
may be possible with anticonvulsants such as carbamazepine, clonazepam, and gabapentin;
however, these are less effective and have significant side effects that may decrease
quality of life. These treatments may be used transiently while optimizing the patient
prior to surgical decompression.
Using the important findings in this study, providers may have informed discussions
with patients about the risks and benefits of an MVD. When consenting patients with
diabetes or higher BMI, it may be prudent to discuss potential increased risk of reoperation
and the risks that may follow. It may even warrant preventative measures prior to
surgery to decrease this risk such as optimizing blood sugar levels, reducing HgA1c
levels < 6%, and encouraging weight loss.[33 ]
[34 ]
[35 ] Weight loss may even improve postoperative refractory/recurrent pain outcomes.[16 ] Alternative intervention strategies may also be worthy of discussion given the risks
of reoperation and should be discussed with the patient.
Limitations
The ACS-NSQIP is a national database, but there still is potential for selection bias
related to nonrandomized participation of institutions. The ACS-NSQIP only reports
30-day postoperative outcomes, which narrows the interpretation of our results to
a short postoperative period. The reoperation rate in the NSQIP cohort was 3.2%, which
is lower than other reported reoperation rates. This limitation is particularly important
when considering persistent/recurrent pain after a failed MVD.
Additionally, postoperative complications were not comprehensively reported in the
NSQIP database. In the context of this study, postoperative pain scores are important
determine the effectiveness of the procedure. The NSQIP database does not report radiosurgery
procedures, preventing a comparison analysis between MVD and SRS. Comparing postoperative
pain outcomes and complications in patients with BMI > 40 receiving either an MVD
or SRS would be an important follow-up study.
The indication for reoperation was also limited based on the provided CPT codes. The
largest category indication for reoperation was the “other/unknown” group, which included
14 different CPT codes. The CPT codes in this group corresponded to indication such
as removal of bone flap, exploratory craniotomy, and cranioplasty. There were also
seven reoperations that were reported as “NA” or not reported. Better characterization
of the indications for reoperation may have increased the sample size in the groups
and may have affected the statistical analysis.
Conclusion
This study demonstrates in a large cohort that the incidence of reoperation in patients
with morbid obesity almost 8%. Patients with morbid obesity are at risk for lengthier
surgery times and wound complications leading to reoperation. Diabetes is also associated
with increased risk of reoperation and wound complications. Patients with morbid obesity
and diabetes have almost a 5 times increased risk of reoperation with a near-linear
relationship of reoperation and procedure duration. Given that patients with morbid
obesity consist of 7% of the population receiving an MVD, these are crucial findings
that may impact a neurosurgeon's practice and potential management. Additional studies
are needed to determine if treatment outcomes in other treatment modalities are equally
efficacious and minimize postoperative complications for patients with morbid obesity.
