Background. We searched -in transverse ultrasound view- the value of the difference (Delta) between -proximal to the tunnel- CSA (a) and -in the tunnel's inlet- CSA (b) for separating normal from abnormal median nerves. Methods. 51 patients –suspicious for CTS- underwent Phalen and Tinnel tests. After that, we used a high frequency ultrasound to measure CSAa, CSAb and Delta CSA in both hands. 33 of our 51 patients did not experience any clinical symptoms at the contralateral hand, so that we could perform a comparative study of normal and pathological median nerves (on the same patients). Then, all of them completed a Q-DASH questionnaire and a visual analogue scale (VAS 100/100) and they carried through with a nerve conduction study (NCS). Results. We found that a CSAb more than 0,010 and a Delta CSA > 0,003 are both very sensitive findings for CTS, but only DeltaCSA has good specificity. Comparing to NCS the Delta CSA>0,003 had no statistical difference in sensitivity, specificity, true negative and true positive results. Furthermore, patients with Delta CSA>0,009 were suffering from heavy CTS according to NCS, Q-DASH and VAS. On the other way, a Delta CSA between 0,003 and 0,006 suggests a mild or moderate CTS. Conclusion. Delta CSA could be the golden standard for the detection of CTS in patients that feel uncomfortable to undergo NCS. We propose a grading scale that distinguish mild or moderate syndromes (where we could try a conservative treatment) from heavy syndromes and help as on decision-making

Aims

We aimed to evaluate the temperature around the nerve root during drilling of the lamina and to determine whether irrigation during drilling can reduce the chance of nerve root injury.

Using the transverse processes of fresh porcine lumbar spines as an experimental model we evaluated the heat generated by a rotating burr of a high-speed drill in cutting the bone. The temperature at the drilled site reached 174°C with a diamond burr and 77°C with a steel burr. With water irrigation at a flow rate of 540 ml/hr an effective reduction in the temperature was achieved whereas irrigation with water at 180 ml/hr was much less effective. There was a significant negative correlation between the thickness of the residual bone and the temperature measured at its undersurface adjacent to the drilling site (p < 0.001).

Our data suggest that tissues neighbouring the drilled bone, especially nerve roots, can be damaged by the heat generated from the tip of a high-speed drill. Nerve-root palsy, one of the most common complications of cervical spinal surgery, may be caused by thermal damage to nerve roots arising in this manner.