Association of biomarker S100B and cerebral oximetry with neurological changes during carotid endarterectomy performed in awake patients.

Background: This study attempted to correlate neurological symptoms in awake patients undergoing carotid endarterectomy (CEA) under local anaesthesia (LA) with serum concentration of S100B protein and measurement of cerebral oximetry with near-infrared spectroscopy (NIRS). Patients and methods: A total of 64 consecutive CEAs in 60 patients operated under LA during an 18-month period were prospectively evaluated. A cerebral oximeter was used to measure cerebral oxygen saturation (rSO2) before and after cross-clamping along with serum concentration of the S100B protein. Selective shunting was performed when neurological changes occurred, regardless of NIRS. Neurological deterioration occurred (neurological symptoms group) in 7 (10.9 %) operations. In 57 (89.1 %) operations, the patients were neurologically stable (no neurological symptoms group). Results: The neurological symptoms that occurred after clamping correlated with an increase in the serum level of S100B (P = .040). The cut-off of 22.5 % of S100B increase was determined to be optimal for identifying patients with neurological symptoms. There was no correlation between rSO2 decline and neurological symptoms (P = .675). Two (3.1 %) perioperative strokes occurred. Conclusions: We found a correlation between neurological symptoms and serum S100B protein increase. However, because of the long evaluation time of serum S100B, this monitoring technique cannot be performed during CEA.

Neurophysiological monitoring of S1 root function during microsurgical posterior discectomy using H-reflex and spinal nerve root potentials.

STUDY DESIGN: Tibial H-reflex and epidural recordings of the spinal nerve root potentials (SRP) of the S1 root were performed intermittently during microsurgical posterior discectomy. OBJECTIVE: To obtain reversible conduction dysfunction of dynamically retracted spinal nerve root S1 in an on-line manner to control the surgical manipulation and prevent iatrogenic root injury. SUMMARY OF BACKGROUND DATA: Excessive force and duration of nerve root retraction during posterior lumbar discectomy may result in additional nerve root injury and battered root syndrome. METHODS: The S1 root was exposed by fenestration and the epidural electrodes were placed along the root above and below the compression site in 12 patients. H wave and SRP changes were recorded intermittently during discectomy and related to different manipulative phases of surgery. The desynchronisation index of SRP was computed off-line as a ratio between a/b, where a represents the positive deflection of the signal from the zero line and b represents peak-to-peak amplitude. RESULTS: The reflex muscle evoked potential from the soleus muscle (H wave), SRP1 (ascendant) and SRP2 (descendant volley) paralleled the surgical manipulation. The amplitude of the H wave significantly decreased and the desychronisation index of SRP1 (later evaluated in 8/12 patients) significantly increased after mobilization of the root with a dissector and in the late phase of intervertebral disc evacuation (P < 0.001), indicating conduction dysfunction related to surgical manipulation of the root. CONCLUSION: A good surgical outcome as shown by preserved Achilles tendon and H reflexes was related to the immediate return of H wave and SRP on stopping the harmful manipulation, and preservation of the H wave and SRP at the end of surgery.SRP monitoring brings up additional information concerning initial root injury and cumulative manipulative effects. The technique of dynamic nerve root retraction in posterior lumbar discectomy can therefore be made safer.

H wave and spinal root potentials in neuromonitoring of S1 root function during evacuation of herniated disc: preliminary results.

AIM: To determine the changes in the tibial H reflex and spinal nerve root potentials (SRPs) of the S1 root during posterior discectomy and the effects of surgical manipulation. METHODS: Tibial H reflex responses (M and H waves) were intermittently recorded from the soleus muscle by surface electrodes during different stages of surgery in 5 patients with S1 radiculopathy. All patients had Achilles reflex preserved bilateraly and no paresis on manual strength testing preoperatively. SRPs were additionally obtained by direct epidural recordings from the surgically exposed S1 root in 2 of them. RESULTS: The variations in the amplitude of H wave were minor and reversible upon the cessation of surgical manipulation of the root, but the H reflex was not lost either temporarily or permanently in any of the patients. Prolongation of H wave latency by up to 18% at the end of surgery in comparison with preoperative value was noticed in 4 patients. However, there was increased degree of desynchronization of the SRP in some phases of the spinal root manipulation, such as root mobilization before the disc incision and retraction during the disc evacuation. H waves and SRPs were continuously present during the surgery. Ankle jerks were preserved postoperatively in all 5 patients. CONCLUSION: Unremarkable variations in H wave latency may be followed by increased SRP desynchronization. Monitoring of the epidurally recorded SRPs seems to be more sensitive to surgical manipulations of the spinal nerve root than the tibial H reflex recordings from the soleus muscle.