Direct cortical stimulation with cylindrical depth electrodes in the interhemispheric fissure for leg motor evoked potential monitoring.

OBJECTIVE: To evaluate cylindrical depth electrodes in the interhemispheric fissure as an alternative to subdural strip electrodes for direct cortical stimulation (DCS) leg motor evoked potential (MEP) monitoring. METHODS: A cylindrical depth electrode was positioned in the interhemispheric fissure of 37 patients who underwent supratentorial brain surgery. Leg sensory and motor cortices were localized by highest tibial nerve somatosensory evoked potential amplitude and lowest DCS leg MEP threshold; the lowest-threshold electrode was then used for DCS leg MEP monitoring. RESULTS: Intraoperative leg MEPs were obtained from all the patients in the series. The mean intensity applied for leg MEP monitoring with the cylindrical depth electrode was 15.2 ± 4.0 mA. No complications secondary to neurophysiological monitoring were detected. CONCLUSIONS: Lower extremity MEPs were consistently recorded using a multi-contact cylindrical depth electrode in the interhemispheric fissure by DCS. SIGNIFICANCE: Cylindrical depth electrodes may be a safe and effective alternative for DCS in the interhemispheric fissure, where subdural strips are difficult to place.

Cerebrospinal fluid levels of tumor necrosis factor alpha and aquaporin 1 in patients with mild cognitive impairment and idiopathic normal pressure hydrocephalus.

OBJECTIVE: The aim of the present work was to make a comparative analysis of the cerebrospinal fluid levels of Tumor necrosis factor (TNFα) and aquaporin 1 (AQP1) in (i) healthy elder control, (ii) patients with mild cognitive impairment and, (iii) patients with idiopathic normal pressure hydrocephalus. PATIENTS AND METHODS: Samples of CSF were taken from seven patients with MCI, 77 years average age; six patients with iNPH, 75 years average age; eleven healthy subjects, 60year average age, were used as controls. The cerebrospinal fluid levels of AQP1 and TNFα were studied by enzyme immunoassay (ELISA). RESULTS: In mild cognitive impairment the total protein content of the CSF and the relative CSF levels of AQP1 and TNFα were similar to those of control subjects and different from those of iNPH patients. On the other hand, in iNPH patients the CSF content of proteins was low and the levels of TNFα were significantly high while those of AQP1 were insignificantly high. CONCLUSION: These finding may help the differential diagnosis and prognosis of mild cognitive impairment and normal pressure hydrocephalus patients.

Delayed Abdominal Pseudohernia in Young Patient After Lateral Lumbar Interbody Fusion Procedure: Case Report.

OBJECTIVE: To describe a rare complication of the extreme lateral interbody fusion technique. BACKGROUND: Lateral lumbar interbody fusion (LLIF) is a minimally invasive technique that has achieved great reputation among spine surgeons because of its advantages over other procedures. However, complication rates of this technique have not been definitively assessed so far. CASE REPORT: A 44-year-old male smoker, presenting with pseudoarthrosis of a previous posterior stabilization, underwent an LLIF procedure. The operation was uneventful, and an appropriate functional recovery was achieved by 2 months after surgery. Nevertheless, 5 months after surgery, the patient developed pulmonary tuberculosis and a mass in the proximity of the LLIF incision appeared. This mass was finally diagnosed as abdominal pseudohernia and had to be surgically repaired. CONCLUSIONS: Abdominal pseudohernia is a rare complication of LLIF procedures. The interest of the present case is 3-fold: 1) it is the first delayed case of abdominal pseudohernia after an LLIF procedure; 2) it is the first case described in a young patient in whom risk factors have been identified and discussed; and 3) it is the first case that did not resolve spontaneously and required surgical repair. This exceptional complication must be borne in the mind of the spine surgeon when using the LLIF technique, and special precautions, such as laxatives or respiratory physiotherapy, apart from meticulous atraumatic dissection and closure of the abdominal wall and specific intraoperative monitoring, should be taken in high-risk patients to prevent it.

Transoral vertebroplasty for a C2 aneurysmal bone cyst.

BACKGROUND CONTEXT: Aneurysmal bone cysts at the cervical spine represent a real challenge both diagnostically and therapeutically, especially in young patients. PURPOSE: We present an unusual case of a C2 aneurysmal bone cyst expanding in the entire vertebral body in a girl successfully treated with a transoral vertebroplasty. STUDY DESIGN: This is a case report study. METHODS: We report the case of a 17-year-old girl with a history of cervical pain and occipital headache after a car accident. Routine x-rays disclosed a C2 lesion. Her neurologic examination was normal. Computed tomography showed a lytic lesion occupying almost the entire body of the C2 vertebra. The cortical bone was intact but notably thinned. Magnetic resonance imaging revealed a cystic image with blood inside. Transoral vertebroplasty was selected among other surgical options for the following reasons: (1) to improve the clinical symptoms, and (2) to prevent future vertebral collapse with devastating neurologic consequences. Under general anesthesia and continuous neurophysiological monitoring, we conducted a fluoroscopic-guided transoral vertebroplasty through a Jamshidi needle. A cytology sample from the cystic lesion was taken through the needle. RESULTS: The blood smear showed no tumoral cellularity. There were no complications during surgery or postoperative infections. After 4 years of follow-up, the patient is pain-free and leads a normal life. CONCLUSIONS: Transoral vertebroplasty seems to be a direct, safe, and effective technique to stabilize cystic lesions that endanger the stability of C2 and to improve symptoms. Aneurysmal bone cysts should be included in the differential diagnosis of lytic lesions at the C2 vertebral body.

Electrical stimulation threshold in chronically compressed lumbar nerve roots: Observational study.

OBJECTIVES: Intraoperative neuromonitoring (IONM) is a common practice in spinal surgery, mostly during pedicle screw placement. However, there is not enough information about the factors that can interfere with IONM data. One of these factors may be existing damage of the nerve root whose function must be preserved. The main purpose of the present study is to evaluate the effect of chronic compression in lumbar nerve roots in terms of stimulation thresholds during direct nerve stimulation. PATIENTS AND METHODS: Direct electrical stimulation was performed in 201 lumbar nerve roots during lumbar spinal procedures under general anaesthesia in 80 patients with different lumbar spinal pathologies. Clinical and radiological data were reviewed in order to establish the presence of chronic compression. RESULTS: Chronically compressed nerve roots showed a higher stimulation threshold than non compressed nerve roots (11.93 mA vs. 4.33 mA). This difference was confirmed with intra-subject comparison (paired sample t test, p=0.012). No other clinical factors were associated with this higher stimulation threshold in lumbar nerve roots. CONCLUSION: A higher stimulation threshold is present in compressed lumbar nerve roots than non compressed roots. This needs to be taken into consideration during pedicle screw placement, where intraoperative neurophysiological monitoring is being used.

Role of multimodal intraoperative neurophysiological monitoring during positioning of patient prior to cervical spine surgery.

OBJECTIVE: To determine the use of multimodal intraoperative neurophysiological monitoring (IONM) during positioning procedures in cervical spine surgery. METHODS: IONM data was collected from 75 patients from the onset of positioning to the end of the surgical procedure. These included: transcranial motor evoked potentials (TcMEP), somatosensory evoked potentials (SEP) and free running electromyography (EMG) recordings. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (PNV) were calculated. RESULTS: IONM warnings were given in 5 cases during neck positioning. These consisted of the disappearance of TcMEP in all the cases, while two cases showed a loss of SEPs as well. Four of these patients presented a complete recovery of TcMEP and SEPs after neck repositioning. The patient in which this recovery was not present, woke up with new postoperative neurological deficits. Sensitivity, specificity, PPV and NPV of TcMEP during cervical positioning were all 100%. Sensitivity of SEPs was 40%; specificity and PPV were 100%; and the NPV of SEPs was 95.9%. CONCLUSION: Multimodal IONM is a useful method to prevent spinal cord injury during neck positioning in cervical spine surgical procedures. TcMEPs showed the highest sensitivity in detecting injuries to cervical spine related to neck positioning. SIGNIFICANCE: Multimodal IONM should not only be considered for detecting intra-operative warnings, but also during positioning.