Surgical outcomes in very advanced CTS
There have now been several studies of outcome in patients with ‘extremely severe’ CTS as defined by an absent surface motor potential from abductor pollicis brevis, though as is usual with studies of the outcome of surgery for CTS, the outcome measures vary. Nevertheless there is a considerable degree of agreement amongst the studies – the outcomes are not as good as those obtained in milder CTS, but neither is surgery futile and results can be excellent in well selected cases.
Mondelli 2001 – studied 10 patients and followed them up for 6 months after surgery. 8 patients regained some recordable motor activity in APB (by needle examination) though thenar atrophy persisted in all. Functional status improved overall. These patients were selected for surgery because of severe pain and this resolved in all cases. No overall patient satisfaction was reported.
Nobuta 2005 – studied 50 hands with clinically defined severe CTS – thenar atrophy and loss of thumb opposition. 43 of these hands had unrecordable surface motor potentials from APB but their results are not given separately. Patients were followed up for at least 6 months. This study is interesting for also reporting the median motor potential from the second lumbrical muscle which was recordable in all 50 hands. The overall outcomes were described as excellent in 28 hands, good in 16 hands, fair in 6 hands, corresponding to my ‘cured’, ‘much improved’ and ‘slightly improved’ categories, giving an overall success rate of 88%. Excellent results were significantly less likely where the distal motor latency to the second lumbrical was >=10 msec (20% vs 65%)
Capasso 2009 – followed up 37 patients for periods ranging from 12-95 months. These fell into three groups, 13 were considered to have a specific cause for their CTS and analysed separately. The remainder were felt to be ‘idiopathic’ and 12 had been treated surgically and 12 conservatively or not at all. None of the untreated/non-surgical group had shown any neurophysiological improvement but one patient did report resolution of pain/tingling. Of the surgically treated group all but 1 showed both symptomatic and neurophysiological improvement but probably only one patient had a fully normal hand both subjectively and on examination at follow-up. This study did report overall patient satisfaction with surgery – complete cure in 3 hands, much improved in 8 hands and slightly better in 3 hands – which I would take as a 78% success rate. Of the 6 patients whose CTS was thought to be related to other pathology, mostly diabetes, and operated only 2/7 hands had a successful overall outcome.
Tatsuki Ebata has concentrated particularly on the recovery of the movement of thumb opposition (Ebata 2012, Ebata 2014). He was able to review 109 operated hands, a year or more after surgery, where the motor potential from APB had been unrecordable beforehand. Satisfactory thumb opposition returned in 57 hands (52%). There were few predictors of recovery but results were better in younger patients – 92% recovery in those under 50, 47% in those aged 50-59, 50% in patients aged 60-69 and 45% in those aged 70 years or more. He then went on to study a group of 41 hands with serial NCS after surgery to compare functional with neurophysiological recovery. 58% of these hands recovered thumb opposition though 78% showed some neurophysiological recovery. Patients who showed re-appearance of the surface motor potential from APB within 6 months of surgery were much more likely to regain functional thumb opposition (100%) then those in whom neurophysiological recovery took more than 6 months (15%) and no patient with an unrecordable APB motor potential at 12 months post surgery recovered opposition.
An additional concern when there is actual loss of nerve fibres as a result of severe CTS is that recovery after relief of the compression requires regrowth of damaged nerve fibres. Such regenerated nerve fibres may be hypersensitive and in such cases 'recovery' may mean that the patient experiences tingling and pain where before they had only numbness. A study of 276 elderly patients (Papaloizos 2010) found this pattern of recovery in 23 (8%). Patients suffering this complication tended to have more severe neurophysiological abnormalities before surgery, and to already have pain before surgery. They suggested that elderly patients with these characteristics should be warned of the possibility of this outcome before surgery.
In Canterbury we have records of outcome for 460 Canterbury grade 6 hands, where grade 6 is defined by the effective absence of a motor potential from APB. The subjective success rate for these is 50% overall, slightly lower when the operation is a second attempt after previous failed surgery (45% - 34 of these operations are second attempts at surgery). The lower overall success rate than that reported by Mondelli, Capasso and Nobuta probably reflects the fact that these are unselected patients and that many of them have other pathology. These results also reflect 'ordinary’ NHS practice – patients being treated in specialist centres as part of trials often have better outcomes, whatever condition you study. We probably now have enough data to study the prognostic utility of the lumbrical motor potential, as suggested by Nobuta, and that may be a project for the future.
As demonstrated by Capasso, it is also the case that nerves this badly damaged are unlikely to improve in any way without surgery so that the choice for the patient comes down to either living with it as it is, or taking a chance on surgery with less than ideal odds of success. One just has to be realistic about what can be expected from surgery at the outset and it is now also worth being aware that good results seem to be less likely in this group if the patient is older, there is other pathology such as diabetes, or if there is a very long distal motor latency to the lumbrical muscle.
If you have extremely severe CTS then the advice may be summarised as follows:
1) If your main symptoms are pain/tingling these can be expected to improve
2) If you are troubled by weakness of the hand this may improve in 50-80% of cases, but will take time
3) Your prospects are worse if you are older or have other problems such as diabetes
4) If your main complaint is numbness there is a modest risk of having more pain/tingling after surgery
Revision date - 22nd November 2014