Cranioplasty in Acoustic Neuroma Surgery†
Presented at the Meeting of the Eastern Section of the American Laryngological, Rhinological and Otological Society, Inc., New York, New York, January 31, 1998.
Objectives To measure the incidence of postoperative headaches after retrosigmoid resections of acoustic neuromas and to evaluate the impact of cranioplasty on the prevention and management of these headaches.
Study Design A prospective evaluation was performed on 30 consecutive patients who underwent a cranioplasty after retrosigmoid excision of their acoustic neuroma. The results were compared with 30 historical control patients who underwent the same procedure but did not have reconstruction with a cranioplasty. The patients were evaluated by review of office records and via telephone questionnaire.
Methods One group of patients (30 patients) had no cranioplasty, and the other group of 30 patients had primary reconstruction with a titanium mesh-acrylic cranioplasty. All 60 patients were asked to report on the duration and severity of their headaches by means of a standard questionnaire, grading their symptoms on a scale of 1 to 4. The data were subjected to χ2 and Student t test statistical analyses.
Results New-onset, postoperative headaches occurred in 27% of patients, 23% in the cranioplasty group compared with 30% in the group without cranioplasty (a difference that was not statistically significant [P = .158]). However, there was a statistically significant difference in the severity of the headaches (P < .03). The headaches in the cranioplasty group were less severe and were not disabling. There were no complications, infections, or extrusions related to the cranioplasty.
Conclusions Cranioplasty has not been able to eliminate postoperative headaches. However, the use of cranioplasty has significantly decreased the severity of postoperative headaches after retrosigmoid excision of acoustic neuromas.
Technological advances, improved surgical skills, and intraoperative monitoring of facial nerve and auditory functions have all helped significantly to improve surgical outcomes in acoustic neuroma surgery. Modern imaging, including magnetic resonance imaging (MRI), has contributed to earlier diagnoses and established the specific, anatomical dimensions of tumors. However, one complication that has received less emphasis than other more life-threatening or disfiguring complications is the development of new-onset, postoperative headaches. Despite recent investigations on the causes and management of postoperative headaches, we still lack a complete understanding of their pathophysiology, how to prevent their occurrence, and how to treat them successfully. The purposes of this study were to measure the incidence of postoperative headaches after retrosigmoid excision of acoustic neuromas and to evaluate the safety and effectiveness of titanium mesh-acrylic cranioplasty in the prevention of such headaches.
MATERIALS AND METHODS
Two groups of patients who underwent a retrosigmoid excision of their acoustic neuroma between 1995 and 1998 were compared. Group I consisted of 30 patients who did not undergo cranioplasty reconstruction, and group II consisted of 30 patients who had reconstruction with a titanium mesh-acrylic cranioplasty. There were 21 women and 9 men in group I, their ages ranging from 25 to 76 years. Group II included 19 women and 11 men ranging in age from 24 to 70 years (Table I). The craniotomy defect was approximately 3 cm in diameter in all patients. The average tumor sizes were 2.6 cm in group I and 1.9 cm in group II.
Table Table 1.. Profile of Patients Enrolled in Study.
After closure of the dura, a cranioplasty was performed routinely in group II by closing the defect with a custom-sized piece of titanium mesh molded with Codman Aneuroplastic type 2 fast-set methylmethacrylate (Johnson & Johnson, Raynham, MA). All patients were operated on by the same surgical team (j.j.w. and m.s.). The patients were contacted either during an office visit or on the telephone by questionnaire. The size of the tumor and the incidence of complications, including postoperative headaches, were noted. The patients were also asked to grade their postoperative headache on a scale ranging from 1 (mild) to 4 (unbearable) and to remark on the length of time during which the headache persisted (Table II). The questionnaires were collected a minimum of 6 months and up to 5 years after surgery. The results were subjected to χ2 and Student t test statistical analyses.
Table Table 2.. Grading System for Preoperative and Postoperative Headaches.
The results are summarized in Table III. Six patients (20%) in group I, who did not receive a cranioplasty, reported preoperative headache, with an average grade of 1.7. Thirteen patients (43%) reported postoperative headaches with an average grade of 2.8. However, only nine patients (30%) reported a new-onset, postoperative headache with an average grade of 3.3. In this group of new-onset, postoperative headaches the pain lasted from 2 months to 4 years.
Table Table 3.. Incidence and Severity Grading of Headaches After Retrosigmoid Excision of Acoustic Neuroma.
Eight patients (27%) in group II, who underwent a cranioplasty, reported preoperative headaches with an average grade of 2.1. Thirteen patients (43%) had postoperative headaches with an average grade of 2.1. Seven patients (23%) reported a new-onset, postoperative headache with an average grade of 2. The headaches lasted from 6 months to 2 years.
There was no significant difference in the incidence of preoperative or postoperative headaches between groups I and II (30% vs. 23%), despite a trend toward more headaches in the group without cranioplasty. However, there was a statistically significant difference in the severity of new-onset, postoperative headaches (P < .03). The headaches in patients in group II (who had cranioplasty) were less severe and disabling than those in the patients in group I (who did not have reconstruction). There was no relation between tumor size, duration of surgery, or incidence of headaches. Two patients had a wound infection; neither had undergone a cranioplasty or reported preoperative or postoperative headaches. None of the patients had meningitis. There was no difference in the incidence of cerebrospinal fluid leak (CSF) between the two groups (three patients in each group). Only one of the patients who had a CSF leak reported worsening of her headache from grade 2 before surgery to grade 4 after surgery. She had undergone a cranioplasty.
The earliest known comprehensive classification of headaches comes from the work of Aretaeus of Cappadocia and dates back to the first century. 1 In 1962 a National Institutes of Health (NIH) ad hoc committee proposed a new headache classification scheme. 2 The International Headache Society (IHS) introduced the latest and most detailed classification of headaches, providing the international community with a standardized set of terminology and criteria describing the quality, timing, frequency, and cause of headaches. 3 The IHS classification, translated into 15 languages, is a more expanded and detailed version of the earlier NIH classification of 1962. Neither classification system includes a separate category for postoperative headaches, which, undoubtedly, should belong in any future versions.
Comparing treatment outcome of headaches requires a grading system that is simple and readily understandable for the individual. However, grading systems can be quite elaborate, such as the Henry Ford Hospital Headache Disability Inventory (HDI), which is based on a 25-item entry questionnaire (down from 40 items). 4 For the purpose of the present comparative study, we have chosen to use a more simplified, four-item grading system similar to those used in previous studies. 5–7
The reported incidence of postoperative headaches after acoustic neuroma surgery appears quite diverse, with wide variations reflected in different studies. Schessel et al. 8 reported a 63.7% incidence of “significant local discomfort and headache” in 58 patients who underwent suboccipital excision of their acoustic neuroma, while none of their 40 matched patients who underwent a translabyrinthine excision had such symptoms. However, Pedrosa et al. 9 reported a 73% incidence of headaches in the suboccipital group versus a 53% incidence in the translabyrinthine group. In reviewing 321 patients who underwent a retrosigmoid excision, Harner et al. 5 reported the incidence of postoperative headaches to be 23% at 3 months, 16% at 1 year, and 9% at 2 years. In an extensive multi-institutional review of 1579 patients entered in the acoustic neuroma registry, Wiegand et al. 10 reported a 17% incidence of postoperative headaches. They found no significant difference in headache scores between the translabyrinthine and the posterior-fossa procedures.
The pathophysiology of postoperative headaches continues to evade us. Vijayan 11 reported on the clinical characteristics of postoperative headaches after acoustic neuroma surgery, suggesting a combination of tension-type, neuralgic, and vascular components. In a case study Hendler et al. 12 proposed cell-membrane instability as an explanation of postoperative headaches based on the patient's response to divalproex sodium. Catalano et al. 13 concluded in their study that free circulation of bone dust might be the most important factor in the development of postoperative headaches. Another possible cause is the adherence and scarring of the subcutaneous soft tissues and muscle to the underlying dura.
Cranioplasty appeared to provide the solution to headaches resulting from dural scarring and adhesions. Schessel et al. 14 reported a significant reduction of postoperative headaches with placement of a bone flap. Harner et al. 6 performed a cranioplasty with methylmethacrylate to reduce the incidence of postoperative headaches. They reported a 4% incidence of headache in the cranioplasty group compared with 17% in a matched group with no cranioplasty. Soumekh et al. 7 found cranioplasty to be helpful in reducing the incidence of debilitating postoperative headaches. In their analysis of postoperative headaches, Ruckenstein et al. 15 reported that within the first postoperative year, patients undergoing suboccipital craniotomies had significantly more postoperative pain than those who underwent translabyrinthine resections, despite the use of a cranioplasty. However, by 1 year after surgery, the difference was no longer significant.
We have been routinely performing titanium mesh-acrylic cranioplasty as described by Malis 16 in all our retrosigmoid acoustic neuroma resections since 1997. The free-floating bone-dust theory is unlikely to explain the postoperative headaches in our patients, because of our regular, conscientious effort to irrigate and suction out all visible bone dust in every case. The theory of subcutaneous tissue and muscle attachment to the underlying dura causing headache appeared to provide a reasonable explanation for these headaches. A significant advantage of the titanium-acrylic method is that it is quick, with minimal extraoperative time. The combination of titanium with acrylic creates a far stronger cranioplasty than either product used alone. 16 Furthermore, the titanium mesh is nonmagnetic, radiolucent, and highly biocompatible. Patients with this type of cranioplasty have had no infections or extrusions and are able to undergo MRI and computed tomography (CT) scans without difficulty.
We found no significant difference in the overall incidence of new-onset, postoperative headaches between the two groups in the present study. However, there was a statistically significant difference in the severity of the headaches. Patients who underwent a cranioplasty had milder headaches. The incidence of grade 4, disabling headaches was higher in our patients in group I, who did not have reconstruction. Nevertheless, seven of our patients in group II who underwent a cranioplasty did complain of postoperative headaches with an average grade of 2. These results suggest that the their headaches are neither the result of dural pull nor the result of bone dust in the cerebellopontine angle. The cause of their headaches remains elusive. The severity of the headache in the patient with a cranioplasty who has had persistent symptoms after 1 year was graded as 1 (mild, minor annoyance) compared with a grade of 2 (moderate, almost daily) and a grade of 4 (incapacitating, disabling) in two patients without a cranioplasty. Only one patient with a grade 4 headache in the group without reconstruction required narcotics to control the pain. The rest of these patients responded well to aspirin or acetaminophen.
The medical treatment of postoperative headache relies on the choice of the appropriate drug for the individual patient. The different drug categories include aspirin, acetaminophen, nonsteroidal anti-inflammatory medications, muscle relaxants, antidepressants, anticonvulsants, and combination medications. It is not advisable, and often unnecessary, to resort to narcotics in the treatment of these headaches because of their chronicity and hence the addictive potential of these drugs. Patients with severe, uncontrollable headaches need the multidisciplinary assistance of a pain-management team including a psychiatrist or clinical psychologist, a neurologist, and a physical rehabilitation specialist.
In addition to potentially controlling or lessening the impact of postoperative headaches after retrosigmoid acoustic neuroma resections, cranioplasty helps restore the contour of the surgical defect, improving its feel and appearance. Patients are not troubled by the progressively deepening postmastoid groove traditionally seen in patients without cranioplasty.
The causes of postoperative headaches after retrosigmoid acoustic neuroma resections are not yet fully evident. Cranioplasty may play a role in preventing or reducing headaches that are due to dural adhesions to nuchal muscles and to subcutaneous tissues. Clearly, cranioplasty has not eliminated postoperative headaches, raising further questions about the pathophysiology of these headaches. However, in this study cranioplasty has been shown to decrease the severity of headaches in the group having reconstruction. Titanium mesh-acrylic cranioplasty is a fast, safe way to reconstruct surgical, cranial defects with the added benefit of the improved feel and appearance of the retrosigmoid area.