Impact of pain and postoperative complications on patient-reported outcome measures 5 years after microvascular decompression or partial sensory rhizotomy for trigeminal neuralgia

Trigeminal neuralgia (TN) presents with severe, unilateral, electric shock-like facial pain provoked by light touch, resulting in significant social disability and associated anxiety and depression [1, 2]. Treatment with anticonvulsant drugs provides some patients with prolonged pain relief and acceptable quality of life. For other patients, the variety of surgical techniques available for TN provide the longest period of pain relief, with a low but significant morbidity and mortality [3‐5]. These include invasive posterior fossa procedures, such as microvascular decompression (MVD), partial sensory rhizotomy (PSR), or more recently, internal neurolysis. If neurovascular compression (NVC) is found on magnetic resonance imaging (MRI), MVD is performed, with the aim of decompressing the trigeminal nerve in the region of the root entry zone, where pressure from major arterial vessels is most likely to occur. PSR or internal neurolysis are only carried out if no NVC is found. PSR entails the division of the lateral part of the sensory root, whereas internal neurolysis entails separating nerve fibres longitudinally, and it is postulated that the latter causes less injury to the nerve. PSR, therefore, has become less common [4].

Despite the range of surgical techniques on offer for TN, there are few randomised controlled trials of their efficacy, and existing cohort studies are usually retrospective and of poor quality [6]. These studies do not use standardised outcome measures, making results hard to interpret and compare, resulting in difficulty for patients in choosing between surgical techniques [7, 8]. The primary outcome measure used in many surgical studies for TN is pain relief with or without medication, with neglect of patient-reported outcome measures (PROMs) such as quality of life. Use of PROMS may highlight the potential benefits of posterior fossa procedures for TN over medical management [6]. PROMs to measure pain and its impact have been used in TN, but the impact of other factors on quality of life, such as the fear of return of pain after MVD, or the incidence of numbness after destructive procedures like PSR, is unexplored [9, 10]. A systematic assessment and comparison of the effect of these postoperative complications on quality of life is needed.

This cross-sectional study is reported in accordance with the STROBE checklist for observational studies [11]. Ethical approval was given by Frenchay Hospital Bristol LREC (Project Number 2001/60).

This prospective study assessed all patients with TN a mean 5 years after MVD or PSR using a range of PROMs, including SF-12, the HADS and questions about postoperative complications. The results varied according to the PROM used. Patients’ responses supported our main hypothesis, that PSR, given its higher rate and severity of complications [12], is associated with poorer quality of life and that pain recurrence is not the only factor impacting on quality of life. The SF-12 showed that the physical and mental dimensions of quality of life were lower in patients 5 years after posterior fossa surgery than UK norms from 2012. The SF-12 did not significantly differ between MVD and PSR, though patients were over 3 times more likely to have case-level anxiety on the HADS after PSR than after MVD.

This is the first study to prospectively compare long-term PROMs between two posterior fossa procedures for the treatment of TN. Survey and data collection were carried out by a physician, neurosurgeon and patient, all of whom were independent of the surgical unit. Patients with co-morbidities unrelated to facial pain were also included, ensuring the cohort was as representative of the TN population as possible. However, our study is not without limitations. As PSR is less commonly performed than MVD, the number of patients in the PSR group is relatively small, and so the comparison between the two procedures should be interpreted with caution. Though the four most common postoperative complications are reported in this cohort, this does not accommodate for other complications, such as hearing loss, headaches, dizziness or visual problems, which may impact PROMs and account for the low SF-12 scores in both surgical groups [20, 21]. The HADS has come under increasing criticism for an unstable structure that affects interpretability [22]. The decision to score anxiety and depression separately and categorically was taken before these problems became clear, but made patient distress hard to interpret. Not all patients completed every item of the SF-12, which means for 22 patients after MVD and seven patients after PSR, the SF-12 PCS and MCS could not be calculated.

Other studies have also compared MVD and PSR, but comparison with these is difficult to make due to their focus on pain relief with or without presence of complications [23‐29]. Some studies found that postoperative complications are more frequent after PSR than MVD, but others found that the destructive procedure yields similar pain outcomes and equivocal postoperative complications. Our results suggest that patients after PSR are more anxious and have more frequent postoperative complications, which have a greater severity and impact on quality of life than MVD. The high incidence of complications and numbness in this cohort is consistent with previous reports of PSR [30]. As demonstrated by patient responses, postoperative complications such as numbness and burning can seriously affect quality of life, and this is also reported after stereotactic radiosurgery (SRS) [31]. Though these complications are well reported after destructive procedures, their presence and frequency after MVD in our cohort was surprising. It was demonstrated that 14.6% of patients undergoing MVD may develop numbness, which is milder than after PSR, but can impact on quality of life. Previous studies have shown neurosensory disturbance after MVD, including numbness and change of taste [20, 21]. Only one study in a cohort of patients used the Japanese version of the SF-36 to assess quality of life after MVD [32]. In this study, the individual norm-based items: physical role, emotional role and social functioning were significantly lower than the Japanese population 2 years after MVD, similar to our comparison with the UK population sample. The only other two studies assessing quality of life after surgery for TN reported individual norm-based items of the SF-36 after SRS. Azar and colleagues [33] found improved SF-36 scores after SRS, with a mean follow-up of 54 months. Pan and colleagues [34] found higher scores for individual items of the SF-36 to be associated with lower pain severity, but did not report on other complications. Comparison to these studies is difficult, because of their use of individual items of the SF-36, rather than calculation of PCS and MCS.

Posterior fossa procedures aim to provide immediate pain relief for TN. MVD is considered the procedure of choice for classic TN with NVC, but in patients without NVC, with TN relapsing after MVD or in patients with a vascular anatomy that prohibits safe decompression, destructive procedures such as PSR have been considered a safe and effective alternative [30]. Although PSR has largely been discontinued in routine clinical practice, internal neurolysis is now advocated in those with no NVC but, as with PSR, the incidence of numbness after internal neurolysis is high [4]. Neurosensory disturbance of the trigeminal nerve results in poorer health-related quality of life [35], as found in our study. There have been no head-to-head comparisons of PSR against internal neurolysis, but as they are both destructive procedures, surgeons must warn patients of the increased risk of complications, such as numbness, and their impact on anxiety and wellbeing to ensure informed consent has been obtained. The difference between SF-12 scores of patients and English norms from 2012 is concerning. This may be due to postoperative complications and recurrence of pain, but may also be due to fear of the return of pain, which was not assessed in this study. In TN, there is risk of development of depressive, anxiety or sleep disorders [1], which also reduces quality of life compared to the general population, and there is no evidence to suggest that posterior fossa surgery alleviates these. Regardless of the reasons for poorer quality of life in these patients, these results suggest unmet needs after surgery, and in this respect and as previously suggested, that the current management of TN is suboptimal [36]. Future studies should seek to determine whether posterior fossa surgery reduces the incidence of anxiety, depression and fear of recurrence in TN more effectively than other modalities, such as medications and Gasserian ganglion surgery. In this cohort, though the patients’ responses revealed PSR to yield more common and severe complications that impact quality of life, this was not reflected by the SF-12. This may be because the SF-12 provides a generalised measure of the physical and mental dimensions of quality of life, and is not sensitive to the impact of these postoperative complications after surgery for TN. Therefore, the next step is to determine from patients themselves what outcomes they consider important, often divergent from those routinely assessed, and to estimate minimally important clinical differences, as has been done for SRS patients [37, 38]. A recent review identified over 116 quality of life scales that were categorised into 32 health domains [39]. Ideally a quality of life scale not only represents patients’ priorities but can also be translated into quality-adjusted life years, which in turn, can be represented in economic terms to guide treatment choices [40]. As TN is managed by a wide variety of medical and surgical interventions, arriving at a consensus for what constitutes the best quality of service would be of considerable value, as has been done for headaches [41].

In conclusion, PSR was associated with a higher risk of postoperative complications than MVD, which was associated with anxiety and impacted patients’ rated quality of life, although this was not detected by the SF-12. The quality of life of postoperative patients with TN is lower than that of the age-matched English population, regardless of the surgical procedure, suggesting that this disorder should be regarded as a long-term condition. Patient-centred outcomes and their assessment in TN remains an under-researched area, but one of considerable clinical and economic importance.