Transcranial magnetic stimulation in the semi-quantitative, pre-operative assessment of patients undergoing spinal deformity surgery.

PURPOSE: To compare measurements of motor evoked potential latency stimulated either magnetically (mMEP) or electrically (eMEP) and central motor conduction time (CMCT) made pre-operatively in conscious patients using transcranial and intra-operatively using electrical cortical stimulation before and after successful instrumentation for the treatment of adolescent idiopathic scoliosis. METHODS: A group initially of 51 patients with adolescent idiopathic scoliosis aged 12-19 years was evaluated pre-operatively in the outpatients' department with transcranial magnetic stimulation. The neurophysiological data were then compared statistically with intra-operative responses elicited by transcranial electrical stimulation both before and after successful surgical intervention. MEPs were measured as the cortically evoked compound action potentials of Abductor hallucis. Minimum F-waves were measured using conventional nerve conduction methods and the lower motor neuron conduction time was calculated and this was subtracted from MEP latency to give CMCT. RESULTS: Pre-operative testing was well tolerated in our paediatric/adolescent patients. No neurological injury occurred in any patient in this series. There was no significant difference in the values of mMEP and eMEP latencies seen pre-operatively in conscious patients and intra-operatively in patients under anaesthetic. The calculated quantities mCMCT and eCMCT showed the same statistical correlations as the quantities mMEP and eMEP latency. CONCLUSIONS: The congruency of mMEP and eMEP and of mCMCT and eCMCT suggests that these measurements may be used comparatively and semi-quantitatively for the comparison of pre-, intra-, and post-operative spinal cord function in spinal deformity surgery.

Effect of locally administered ciliary neurotrophic factor on the survival of transected and repaired adult sheep facial nerve.

OBJECTIVE: to determine whether the administration of Ciliary Neurotrophic Factor (CNTF) at the site of repaired facial nerve enhances regeneration in the adult sheep model. METHODS: Ten adult sheep were divided into 2 groups: control and study group (CNTF group). In the CNTF group, the buccal branch of the facial nerve was transected and then repaired by epineural sutures. CNTF was injected over the left depressor labii maxillaris muscle in the vicinity of the transected and repaired nerve for 28 days under local anesthesia. In the CNTF group, the sheep were again anesthetized after nine months and the site of facial nerve repair was exposed. Detailed electrophysiological, tension experiments and morphometric studies were carried out and then analyzed statistically. RESULTS: The skin CV min, refractory period, Jitter and tension parameters were marginally raised in the CNTF group than the control but the difference was statistically insignificant between the two groups. Morphometric indices also did not show any significant changes in the CNTF group. CONCLUSION: CNTF has no profound effect on neuronal regeneration of adult sheep animal model. KEYWORDS: CNTF; Neurtrophic factors; Sheep; Facial nerve; Regeneration.

Sutureless repair of the facial nerve using biodegradable glass fabric.

OBJECTIVES/HYPOTHESIS: To compare a sutureless method of facial nerve repair using a biodegradable glass fabric with the standard method of microsurgical suture. STUDY DESIGN: The facial nerve was transected in groups of six sheep and repaired by either entubulation with a biodegradable glass fabric or standard microsurgical epineurial suture repair. METHODS: Both methods of repair were compared with each other and with a normal control group using electrophysiological and morphometric analysis. RESULTS: Maximum conduction velocity, axon and fiber diameter, and myelin-sheath thickness were all reduced in the repaired nerves when compared with the normal nerves. There was no significant difference among any of the outcome variables between the repair groups. CONCLUSIONS: Repair of nerve injuries by entubulation has several theoretical advantages over standard suture repair: less trauma to nerve ends, no need for microsurgical skills, and delivery of neurotrophic growth factors. It is concluded that repair of the facial nerve by glass-wrap entubulation offers an alternative to standard suture repair without the demands of microsurgery on both time and surgical expertise.

Cardiovascular and autonomic nervous effects of edrophonium and atropine combinations during neuromuscular blockade antagonism in sheep.

OBJECTIVE: To study heart rate (HR), arterial blood pressure (BP) and autonomic nervous (AN) effects of edrophonium-atropine combinations during neuromuscular blockade (NMB) antagonism in sheep. EXPERIMENTAL DESIGN: Randomized, prospective and experimental study. ANIMALS: Seventy-eight Scottish blackface ewes; mean age: 4.5 years; mean body mass: 54 kg. METHODS: After induction with IV etomidate (0.5 mg kg(-1)) and midazolam (0.5 mg kg(-1)), anaesthesia was maintained with halothane and NMB produced with atracurium or mivacurium. In the first study (n = 53), the electrocardiographic (ECG), HR, BP and AN effects of low (40 microg kg(-1)) and high (80 microg kg(-1)) atropine doses combined with either of two edrophonium doses (0.5 or 1.0 mg kg(-1)) were investigated. These variables were also measured in a second study when edrophonium (1.0 mg kg(-1)) was administered 5 minutes before atropine (80 microg kg(-1)) and vice versa. Data were analysed using one-way within-subjects and repeated measures anova. RESULTS: In the first study, all combinations reversed NMB but significantly (p < 0.001) increased HR and BP within 2 minutes without arrhythmias. In the second study, edrophonium (1.0 mg kg(-1)) significantly increased HR and BP, saliva flow (n = 1) and lung sounds (n = 3) and caused ECG changes (n = 1). Cardiovascular changes were partially reversed by atropine (80 microg kg(-1)) administered 5 minutes later. Administered first, atropine (80 microg kg(-1)) significantly decreased HR and BP effects which were fully (HR) and partially (BP) reversed by edrophonium (1 mg kg(-1)) administered 5 minutes later. CONCLUSION AND CLINICAL RELEVANCE: The cardiovascular effects of edrophonium and atropine were opposite to those reported in humans and dogs. Edrophonium (0.5 mg kg(-1)) and atropine (80 microg kg(-1)) caused the mildest HR changes without ECG and noncardiac AN disturbances, and is recommended for the antagonism of NMB in sheep.

Lung function in congenital kyphosis and kyphoscoliosis.

OBJECTIVE: To quantify the respiratory compromise in patients with a congenital kyphosis or kyphoscoliosis in whom the major deformity is the kyphosis. METHODS: Forty-one patients with congenital vertebral anomalies resulting in a kyphosis or kyphoscoliosis, in which the kyphosis was the major deformity, and requiring spine surgery were studied retrospectively. The preoperative respiratory function and radiographic spinal assessments were compared. RESULTS: Twenty-two patients (54%) had an impairment of respiratory function: 2 patients (5%) were severely affected, 8 patients (20%) were moderately affected, and 12 patients (29%) were mildly affected. CONCLUSIONS: An increasing severity of kyphosis was associated with a significant increase in respiratory impairment (P<0.005). A more cranial level of the kyphosis, especially above T10, had a significantly greater effect on respiratory impairment (P<0.001). One untreated patient with a severe kyphosis (128 degrees) died from cor pulmonale.

Use of a static magnetic field to promote recovery after peripheral nerve injury.

OBJECT: While pulsed electromagnetic stimulation has been shown to enhance peripheral nerve regeneration, the effect of a static magnetic field on nerve repair is less clear. The aim of this study was to establish what effect an imposed exogenous static magnetic field has on peripheral nerve regeneration after transection and repair. METHODS: Three groups of six adult sheep were used. The first group acted as normal controls. In the second group, the median nerve was divided and immediately repaired by entubulation within a "controlled-release" biodegradable glass tube. In the third group, small magnets were applied to the sides of the biodegradable glass tubes before the median nerve was repaired using these magnetic tubes. The sheep were allowed to recover and were reexamined 10 months later. The animals underwent comprehensive morphometric (cross-sectional morphometry and measurement of internodal lengths), electrophysiological (determinations of stimulated jitter, maximum conduction velocity, refractory period, and F waves), and isometric tension (isometric twitch and tetanic tension) assessments. CONCLUSIONS: Exogenously applied static electromagnetic fields do not enhance peripheral nerve regeneration.

An in vivo study of peripheral nerves in continuity: biomechanical and physiological responses to elongation.

Using an animal model, the in vivo visco-elastic properties of peripheral nerve in continuity were examined. The nerves were stretched by either 1 cm - Group A (8.8% strain) or 2 cm - Group B (16.1% strain). At constant strain, the stress-relaxation curves were plotted. Maximal relaxation was observed in the first 20 min. After 1 h, the decrease in tensions in Groups A and B were 36.8% and 41.8%, respectively. Throughout this hour and for 30 min after the release of tension, regular recordings of nerve blood flow using laser doppler flowmetry and peak nerve conduction velocity were taken. Nerve blood flow was reduced by similar amounts (Group A, 70%; Group B, 78%) by application of traction. On release, however, Group A displayed a reactive hyperaemia (blood flow 151% starting value) while Group B failed to recover (50% starting value at 30 min). Peak nerve conduction velocity was not significantly altered in Group A in response to traction, whereas in Group B the result was a gradual, but significant reduction in peak velocity to 66% starting value. The lack of correlation between blood flow and peak nerve conduction velocity in these studies suggests that ischaemia is not solely responsible for the increased latency.