Quantitative estimation of the recurrent laryngeal nerve irritation by employing spontaneous intraoperative electromyographic monitoring during anterior cervical discectomy and fusion.

STUDY DESIGN: Prospective, clinical study. OBJECTIVE: The objective of our study was to evaluate the role of laryngeal intraoperative electromyography (IEMG) in predicting the development of postoperative recurrent laryngeal nerve (RLN) palsy in patients undergoing anterior cervical discectomy and fusion (ACDF). We also attempted to develop a method to quantify the total IEMG irritation of the RLN. SUMMARY OF BACKGROUND DATA: RLN injury has been recognized as the most common ACDF-associated neurologic injury. It has been postulated, that the employment of laryngeal IEMG may identify the operative events leading to RLN injury and subsequent postoperative palsy. METHODS: Laryngeal IEMG monitoring was performed in 298 patients undergoing ACDF. Preexistent baseline EMG activity, amplitude, and duration of IEMG activity were recorded. The total amount of RLN irritation was expressed as an Irritation Score (IS) applying a specially designed mathematical equation incorporating the amplitude, the duration, and the presence of any baseline EMG irritation. The relationship of IEMG activity with parameters such as the number of operative levels, the duration of the procedure, the presence of any previous neck surgeries, and the type of the used retractor was examined. RESULTS: IEMG activity was recorded in 14.4% of our patients. Postoperative RLN injury occurred in 2.3% of our patients. The sensitivity of IEMG was 100%, the specificity 87%, the positive predictive value 16%, and its negative predictive value 97%. The calculated IS ranged between 0.28 and 3.47 (mean IS: 2.09). Significantly increased IEMG activity was found in patients with previous surgical intervention, patients undergoing multilevel procedures, long-lasting procedures, and cases in which self-retained retractors were used. Likewise, significantly increased IS were observed in patients with previous surgeries and in cases where self-retained retractors were used. CONCLUSIONS: Our study indicates that laryngeal IEMG is a high-sensitivity modality that can provide real-time information and can potentially minimize the risk of operative RLN injury.

Upper-limb somatosensory evoked potential monitoring in lumbosacral spine surgery: a prognostic marker for position-related ulnar nerve injury.

BACKGROUND CONTEXT: Somatosensory evoked potential (SSEP) is used to monitor integrity of the brain, spinal cord, and nerve roots during spinal surgery. It records the electrical potentials from the scalp after electrical stimulation of the peripheral nerves of the upper or lower limbs. The standard monitoring modality in lumbosacral spine surgery includes lower-limb SSEP and electromyography (EMG). Upper-limb SSEP monitoring has also been used to detect and prevent brachial plexopathy and peripheral nerve injury in thoracic and lumbosacral spine surgeries. We routinely monitor lower-limb SSEP and EMG in lumbosacral spine procedures at our institution. However, a few patients experienced postoperative numbness and/or pain in their ulnar distribution with uneventful lower-limb SSEP and EMG. PURPOSE: We hypothesized that the postoperative upper extremity paresis in lumbosacral surgeries may result from compression and/or stretch of the brachial plexus and/or ulnar nerve while the patients were in prone position. Using upper-limb SSEP, we investigated whether we observe any significant change in the SSEP, and if so, whether we can prevent or reduce frequency of postoperative upper extremity deficits. STUDY DESIGN/SETTING: In this prospective study, we monitored upper-limb SSEP, in addition to lower-limb SSEP and EMG, in 230 elective, posterior lumbosacral spinal procedures. All operations were performed by a group of four neurosurgeons. PATIENT SAMPLE: One hundred and thirty-one female and 99 male with an age range of 28 to 86 years between January 2004 and December 2005 were studied. OUTCOME MEASURES: Amplitude and latency of upper-limb or ulnar SSEP were continuously compared with those of the baseline. A greater than or equal to 50% decrease in SSEPs amplitude and/or a greater than or equal to 10% increase in latency were considered to be significant. METHODS: After intubation, patients were positioned prone on Jackson or Andrews spinal table. Anesthesia was maintained with inhalant gas (desflurane or sevoflurane) and propofol infusion with and without minimal infusion of narcotics (fentanyl, sufentanyl, or remifentanil). Intraoperative neurophysiologic monitoring of upper-limb or ulnar SSEP was achieved by continuously recording cortical and subcortical responses after alternate stimulation of the ulnar nerve at the wrist. In our institutional protocol, a greater than or equal to 50% decrease in SSEPs amplitude and/or a greater than or equal to 10% increase in latency were considered to be significant to alert the operating surgeons. When significant changes occurred, the surgeon was immediately notified. Also, reevaluation of vital signs, depth of anesthesia, and patient's position, and technical troubleshootings were subsequently followed. RESULTS: We observed a greater than or equal to 50% decrease in amplitude of ulnar SSEP in 10 patients without significant changes in lower-limb SSEP (peroneal or posterior tibial nerve SSEP) or EMG during surgery. Eight patients had changes in unilateral limbs, and two patients had changes in bilateral limbs. Two patients with significant changes in unilateral limbs showed changes twice. The mean SSEP amplitude for the 14 changes was 29.2+/-3.1% (mean+/-SEM, standard error of mean) of the baseline value at the average surgical time of 60+/-1.5 minutes. With repositioning of the arms, the amplitudes were immediately restored with the average of 70.2+/-7.1% (n=14) of the baseline value. The mean amplitude of upper-limb SSEP was 73.4+/-8.7% (n=12) of the baseline at wound closure. The average surgical time was 154+/-29.2 minutes per case for the 10 patients. There was no documented postoperative upper extremity paresis in all 230 patients. CONCLUSIONS: The present study demonstrates that upper-limb SSEP monitoring could detect position-related ulnar neuropathy in 5.2% of the patients undergoing lumbosacral spine surgery.

Anterior cervical discectomy and fusion associated complications.

STUDY DESIGN: Retrospective review study with literature review. OBJECTIVE: The goal of our current study is to raise awareness on complications associated with anterior cervical discectomy and fusion (ACDF) and their early detection and proper management. SUMMARY OF BACKGROUND DATA: It is known that ACDF constitutes one of the most commonly performed spinal procedures. Its outcome is quite satisfactory in the majority of cases. However, occasional complications can become troublesome, and in rare circumstances, catastrophic. Although there are several case reports describing such complications, their rate of occurrence is generally underreported, and data regarding their exact incidence in large clinical series are lacking. Meticulous knowledge of potential intraoperative and postoperative ACDF-related complications is of paramount importance so as to avoid them whenever possible, as well as to successfully and safely manage them when they are inevitable. METHODS: In a retrospective study, 1015 patients undergoing first-time ACDF for cervical radiculopathy and/or myelopathy due to degenerative disc disease and/or cervical spondylosis were evaluated. A standard Smith-Robinson approach was used in all our patients, while an autologous or allograft was used, with or without a plate. Operative reports, hospital and outpatient clinic charts, and radiographic studies were reviewed for procedure-related complications. Mean follow-up time was 26.4 months. RESULTS: The mortality rate in our current series was 0.1% (1 of 1015 patients, death occurred secondary to an esophageal perforation). Our overall morbidity rate was 19.3% (196 of 1015 patients). The most common complication was the development of isolated postoperative dysphagia, which observed in 9.5% of our patients. Postoperative hematoma occurred in 5.6%, but required surgical intervention in only 2.4% of our cases. Symptomatic recurrent laryngeal nerve palsy occurred in 3.1% of our cases. Dural penetration occurred in 0.5%, esophageal perforation in 0.3%, worsening of preexisting myelopathy in 0.2%, Horner's syndrome in 0.1%, instrumentation backout in 0.1%, and superficial wound infection in 0.1% of our cases. CONCLUSION: Meticulous knowledge of the ACDF-associated complications allows for their proper management. Postoperative dysphagia, hematoma, and recurrent laryngeal nerve palsy were the most common complications in our series. Management of complications was successful in the vast majority of our cases.

Salvage of a failed odontoid screw.

Complications associated with anterior odontoid screw fixation, although not very common can be quite troublesome. We report a patient with early back-out of the implanted screw and its salvage with re-implantation of a longer screw.

Interobservational variation in determining fusion rates in anterior cervical discectomy and fusion procedures.

The fusion rate represents one of the most commonly used criteria for evaluating the efficacy of spinal surgical techniques and the effectiveness of newly developed instrumentation and spinal implants. Reported fusion rates are not frequently supported by adequate information regarding by whom and how fusion was defined. In our prospective study we examined the fusion rate in patients undergoing first time anterior cervical discectomy and fusion for degenerative disease. Separate, well-defined radiographic fusion criteria were used and the 12-month post-operative X-rays were reviewed independently by a neurosurgeon, a neuroradiologist and an orthopedic surgeon, who were not involved in the patients' management. The observed fusion rates were 77.3, 87.8 and 84.7% respectively. Statistical analysis demonstrated concordance rates of 87.8, 91 and 91.4% and Kappa coefficients of 0.585, 0.620 and 0.723 for each pair of evaluators. Another set of ratings of the same radiographs, by the same interviewers, was obtained 6 weeks after the initial one. The reported fusion rates were 78.2% for the neurosurgeon, 87.4% for the orthopedic surgeon, and 86.1% for the neuroradiologist. Statistical analysis demonstrated intra-observer concordance rates of 98.7, 92.2 and 97.9% respectively, while the Kappa coefficients were 0.963, 0.677 and 0.907 for each reviewer. Our findings confirm the necessity of defining and describing criteria for fusion whenever this rate is reported in clinical series. The lack of widely accepted, well-defined criteria makes comparison of these results difficult. The development of a well organized, prospective clinical study in which fusion and outcome will be assessed by both clinical and radiographic parameters could significantly contribute to a more accurate evaluation of overall outcome of cervical spinal procedures.

Surgical treatment of acute type II and rostral type III odontoid fractures managed by anterior screw fixation.

OBJECTIVES: In the present study, the authors comment on their experience with anterior odontoid screw fixation in the management of odontoid fractures, in an attempt to further assess the safety and the efficacy of this procedure. MATERIALS AND METHODS: A retrospective analysis of 50 consecutive patients with reducible type II or rostral type III odontoid fractures, operated at our hospital with anterior odontoid screw fixation. Radiographic bony fusion, complications, and clinical outcome were evaluated. RESULTS: Solid bony fusion was evident in 38 (90.5%) of the patients. One mechanical instrumentation-related complication occurred, without clinical significance. No other major complications related to the procedure were noted. A satisfactory range of motion in the cervical spine was observed in all patients. CONCLUSIONS: Anterior odontoid screw fixation is a safe and effective procedure for the treatment of type II and rostral type III odontoid fractures. Compliance to the specific indications and contraindications of this operation is crucial for optimal outcome.

Results of long-term follow-up in patients undergoing anterior screw fixation for type II and rostral type III odontoid fractures.

STUDY DESIGN: Retrospective analysis of the fusion rate of a group of 38 patients having undergone anterior screw fixation for type II and "shallow" type III odontoid fractures. OBJECTIVE.: To determine primarily the long-term fusion rate after anterior screw fixation and to study the clinical characteristics of patients that have a statistically significant or nonsignificant influence on successful outcome. SUMMARY OF BACKGROUND DATA: Long-term outcome of anterior screw fixation for odontoid fractures has been evaluated in very few studies. This information should be critical for further establishing this technique as a major therapeutic strategy for these cases. METHODS: Thirty-eight patients, 25 males and 13 females (with mean age 48.4 +/- 0.4 years), with type II and rostral type III odontoid fractures, underwent anterior cannulated screw fixation during a 62-month period. Radiologic examination of the cervical spine with plain radiographs was performed at 6 weeks, and 2, 6, 12, and 24 months, while computerized tomography of the upper cervical spine (C1-C3) was obtained at 6 months after surgery. Follow-up was available for 31 patients, and the follow-up time ranged from 39 to 87 months (mean 58.4). RESULTS: Radiographic evaluation of the follow-up group showed satisfactory bony fusion and no evidence of abnormal movement at the fracture site in 27 (87.1%) patients. Pseudarthrosis developed in 4 (12.9%) patients; however, 3 (9.6%) of them without instability and 1 (3.2%) with instability. One (3.2%) patient had an instrumentation failure without instability. CONCLUSIONS: In our series, anterior odontoid screw fixation comprised a safe therapeutic modality with high stability and low mechanical failure rates during short-term and long-term follow-up.

Correlation of the amount of disc removed in a lumbar microdiscectomy with long-term outcome.

STUDY DESIGN: The authors conducted a prospective clinical study. OBJECTIVES: The objectives of this study were to investigate the relationship, if any, of the amount of removed disc in a standard first-time lumbar microdiscectomy and long-term outcome as well as recurrence and postoperative instability rates. SUMMARY OF BACKGROUND DATA: There is lack of data on the amount of disc that needs to be removed during a lumbar microdiscectomy. Anecdotal data and dogmatic recommendations make the subject even more controversial. MATERIAL AND METHODS: A total of 106 patients underwent a standard first-time lumbar microdiscectomy for medically refractory sciatica resulting from a herniated disc. The removed disc material was weighted. All patients were clinically followed for at least 2 years and outcome was evaluated by using pain intensity, presence of physical signs, functional capacity, return to work, and patients' opinion regarding their outcome. RESULTS: The mean amount of disc removed was calculated at 2.1 +/- 0.9 g. Ninety-one patients had an excellent outcome and returned to their preoperative work. Fifteen patients had persistent symptomatology and underwent extensive radiographic workup, which revealed a disc recurrence at the same level in 8 patients and first-degree instability in 3 patients. In the remaining 4 patients, no clinical or radiographic abnormality was proven and the patients were treated conservatively, whereas all of them had applied for disability. No relationship was proven between the amount of the removed disc and the intraoperative blood loss or the intraoperative complication rate. Our statistical analysis showed no correlation between the amount of the removed disc and the long- term outcome, recurrence rate, or postoperative instability. CONCLUSIONS: The degree of disc removal did not influence the outcome or complication rate in our clinical series.

Does intraoperative electromyographic monitoring in lumbar microdiscectomy correlate with postoperative pain?

OBJECTIVES: Our objective was to correlate the findings of intraoperative electromyographic (EMG) monitoring with immediate postoperative pain in patients undergoing lumbar microdiscectomy. METHODS: A total of 112 patients undergoing de novo lumbar microdiscectomy were prospectively randomized into a control group (n = 45) and a study group (n = 67) in which intraoperative EMG monitoring was used. Postoperative pain and postoperative narcotic consumption were recorded for each patient. RESULTS: The presence or absence of EMG monitoring did not influence the level of reported pain in any anatomic area. In the monitored group, the degree of recorded nerve root irritation did not correlate with reported pain or postoperative narcotic consumption. The level of back pain was found to be significantly higher than the level of hip and calf pain (P < 0.0001). CONCLUSIONS: In our study no correlation was found between intraoperative EMG findings and immediate postoperative pain.

Intracranial temperature: is it different throughout the brain?

INTRODUCTION: Accurate knowledge of cerebral temperature is assuming increasing importance, because its manipulation is employed more frequently for cerebral protection. PURPOSE: This prospective clinical study was performed to examine how well intraventricular temperature reflects global cerebral temperature. METHODS: The intraventricular temperature was monitored in 61 patients who were admitted to the neurointensive care unit for various intracranial pathological entities. A temperature probe coupled to an intraventricular pressure monitor was inserted in the lateral ventricle. At the conclusion of the monitoring process, a second intraventricular temperature probe was inserted in the ipsilateral ventricle and the previous one was carefully and gradually removed. During that removal, the intraparenchymal temperature was monitored for 90 minutes at 1-cm intervals throughout the brain parenchyma. RESULTS: The mean intraventricular temperature was 37.84+/-1.03 degrees C, whereas the mean systemic (rectal) temperature was 37.65+/-0.68 degrees C. At 1 cm outward distance from the lateral ventricle, the mean intraparenchymal temperature was 38.21+/-0.32 degrees C, 38.39+/-0.33 degrees C at 2 cm, 38.27+/-0.31 degrees C at 3 cm, 38.26+/-0.29 degrees C at 4 cm, and, finally, 37.9+/-0.50 degrees C at 5 cm. Statistical analysis of the recordings showed no statistically significant differences between the intraventricular and intraparenchymal temperatures and intraventricular and rectal temperatures. No statistically significant correlation was established between the intraventricular temperature and parameters, such as the patient's age, sex, and admitting diagnosis. CONCLUSION: Cerebral temperature was relatively stable through the brain parenchyma in this study. Because intraventricular temperature accurate.