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Matthias F. Oertel, Juliane Hobart, Marco Stein, Vanessa Schreiber, and Wolfram Scharbrodt

Object

In recent years, the importance of intraoperative navigation in neurosurgery has been increasing. Multiple studies have proven the advantages and safety of computer-assisted spinal neurosurgery. The use of intraoperative 3D radiographic imaging to acquire image information for navigational purposes has several advantages and should increase the accuracy and safety of screw guidance with navigation. The aim of this study was to evaluate the clinical and methodological precision of navigated spine surgery in combination with the O-arm multidimensional imaging system.

Methods

Thoracic, lumbar, and sacral pedicle screws that were placed with the help of the combination of the O-arm and StealthStation TREON plus navigation systems were analyzed. To evaluate clinical precision, 278 polyaxial pedicle screws in 139 vertebrae were reviewed for medial or caudal perforations on coronal projection. For the evaluation of the methodological accuracy, virtual and intraoperative images were compared, and the angulation of the pedicle screw to the midsagittal line was measured.

Results

Pedicle perforations were recorded in 3.2% of pedicle screws. None of the perforated pedicle screws damaged a nerve root. The difference in angulation between the actual and virtual pedicle screws was 2.8° ± 1.9°.

Conclusions

The use of the StealthStation TREON plus navigation system in combination with the O-arm system showed the highest accuracy for spinal navigation compared with other studies that used traditional image acquisition and registration for navigation.

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Benedikt W. Burkhardt, Andreas Simgen, Gudrun Wagenpfeil, Philipp Hendrix, Matthias Dehnen, Wolfgang Reith, and Joachim M. Oertel

OBJECTIVE

There is currently no consensus on whether adjacent-segment degeneration (ASD), loss of disc height (DH), and loss of sagittal segmental angle (SSA) are due to anterior cervical discectomy and fusion (ACDF). The purpose of the present study was to assess the grade of segmental degeneration after ACDF and to analyze if there is a difference with respect to clinical outcome, diagnosis, and number of operated levels.

METHODS

A total of 102 patients who underwent ACDF with a minimum follow-up of 18 years were retrospectively identified. At final follow-up, the clinical outcome according to Odom’s criteria, the Neck Disability Index (NDI), and reoperation for symptomatic ASD (sASD) was assessed. MRI was performed, and DH, SSA, and the segmental degeneration index (SDI, a 5-step grading system that includes disc signal intensity, anterior and posterior disc protrusion, narrowing of the disc space, and foraminal stenosis) were assessed for evaluation of the 2 adjacent and 4 adjoining segments to the ACDF. MRI findings were compared with respect to clinical outcome (NDI: 0%–20% vs > 20%; Odom’s criteria: success vs no success), reoperation for sASD, initial diagnosis (cervical disc herniation [CDH] vs cervical spondylotic myelopathy [CSM] and spondylosis), and the number of operated levels (1 vs 2–4 levels).

RESULTS

The mean follow-up was 25 years (range 18–45 years), and the diagnosis was CDH in 74.5% of patients and CSM/spondylosis in 25.5%. At follow-up, the mean NDI was 12.4% (range 0%–36%), the clinical success rate was 87.3%, and the reoperation rate for sASD was 15.7%. For SDI, no significant differences were seen with respect to NDI, Odom’s criteria, and sASD. Patients diagnosed with CDH had significantly more degeneration at the adjacent segments (cranial, p = 0.015; caudal, p = 0.017). Patients with a 2- to 4-level procedure had less degeneration at the caudal adjacent (p = 0.011) and proximal adjoining (p = 0.019) segments. Aside from a significantly lower DH at the proximal cranial adjoining segment in cases of CSM/spondylosis and without clinical success, no further differences were noted. The degree of SSA was not significantly different with respect to clinical outcome.

CONCLUSIONS

No significant differences were seen in the SDI grade and SSA with respect to clinical outcome. The SDI is higher after single-level ACDF and with the diagnosis of CDH. The DH was negligibly different with respect to clinical outcome, diagnosis, and number of operated levels.

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Joachim Oertel, Michail Gen, Joachim K. Krauss, Matthias Zumkeller, and Michael R. Gaab

✓Waterjet dissection enables vessel preservation and a reduction in intraoperative blood loss. Because even minimal bleeding should be avoided during neuroendoscopy, the waterjet device may be a particularly valuable tool in such procedures. The authors used this instrument in experimental endoscopic procedures in 20 cadaveric porcine brains and clinically in four patients with obstructive hydrocephalus. A precise and accurate septostomy was achieved in all of the pig brains. In two patients the hydrocephalus was due to intraventricular hemorrhage, in one a posterior fossa tumor, and in one a cystic craniopharyngioma. In all patients the surgical view was kept clear with waterjet irrigation and suction. Using a pressure setting of 10 bars, the waterjet device successfully perforated the cyst wall of the craniopharyngioma in one patient and the floor of the third ventricle in three patients. The use of the waterjet device in selected endoscopic procedures appears safe, and may help reduce intraoperative bleeding. However, further studies are needed to confirm the utility of the waterjet tool in endoscopy.

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Matthias Oertel, Daniel F. Kelly, David McArthur, W. John Boscardin, Thomas C. Glenn, Jae Hong Lee, Tooraj Gravori, Dennis Obukhov, Duncan Q. McBride, and Neil A. Martin

Object. Progressive intracranial hemorrhage after head injury is often observed on serial computerized tomography (CT) scans but its significance is uncertain. In this study, patients in whom two CT scans were obtained within 24 hours of injury were analyzed to determine the incidence, risk factors, and clinical significance of progressive hemorrhagic injury (PHI).

Methods. The diagnosis of PHI was determined by comparing the first and second CT scans and was categorized as epidural hematoma (EDH), subdural hematoma (SDH), intraparenchymal contusion or hematoma (IPCH), or subarachnoid hemorrhage (SAH). Potential risk factors, the daily mean intracranial pressure (ICP), and cerebral perfusion pressure were analyzed. In a cohort of 142 patients (mean age 34 ± 14 years; median Glasgow Coma Scale score of 8, range 3–15; male/female ratio 4.3:1), the mean time from injury to first CT scan was 2 ± 1.6 hours and between first and second CT scans was 6.9 ± 3.6 hours. A PHI was found in 42.3% of patients overall and in 48.6% of patients who underwent scanning within 2 hours of injury. Of the 60 patients with PHI, 87% underwent their first CT scan within 2 hours of injury and in only one with PHI was the first CT scan obtained more than 6 hours postinjury. The likelihood of PHI for a given lesion was 51% for IPCH, 22% for EDH, 17% for SAH, and 11% for SDH. Of the 46 patients who underwent craniotomy for hematoma evacuation, 24% did so after the second CT scan because of findings of PHI. Logistic regression was used to identify male sex (p = 0.01), older age (p = 0.01), time from injury to first CT scan (p = 0.02), and initial partial thromboplastin time (PTT) (p = 0.02) as the best predictors of PHI. The percentage of patients with mean daily ICP greater than 20 mm Hg was higher in those with PHI compared with those without PHI. The 6-month postinjury outcome was similar in the two patient groups.

Conclusions. Early progressive hemorrhage occurs in almost 50% of head-injured patients who undergo CT scanning within 2 hours of injury, it occurs most frequently in cerebral contusions, and it is associated with ICP elevations. Male sex, older age, time from injury to first CT scan, and PTT appear to be key determinants of PHI. Early repeated CT scanning is indicated in patients with nonsurgically treated hemorrhage revealed on the first CT scan.

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Matthias Oertel, Daniel F. Kelly, Jae Hong Lee, David L. McArthur, Thomas C. Glenn, Paul Vespa, W. John Boscardin, David A. Hovda, and Neil A. Martin

Object. Hyperventilation therapy, blood pressure augmentation, and metabolic suppression therapy are often used to reduce intracranial pressure (ICP) and improve cerebral perfusion pressure (CPP) in intubated head-injured patients. In this study, as part of routine vasoreactivity testing, these three therapies were assessed in their effectiveness in reducing ICP.

Methods. Thirty-three patients with a mean age of 33 ± 13 years and a median Glasgow Coma Scale (GCS) score of 7 underwent a total of 70 vasoreactivity testing sessions from postinjury Days 0 to 13. After an initial 133Xe cerebral blood flow (CBF) assessment, transcranial Doppler ultrasonography recordings of the middle cerebral arteries were obtained to assess blood flow velocity changes resulting from transient hyperventilation (57 studies in 27 patients), phenylephrine-induced hypertension (55 studies in 26 patients), and propofol-induced metabolic suppression (43 studies in 21 patients). Changes in ICP, mean arterial blood pressure (MABP), CPP, PaCO2, and jugular venous oxygen saturation (SjvO2) were recorded. With hyperventilation therapy, patients experienced a mean decrease in PaCO2 from 35 ± 5 to 27 ± 5 mm Hg and in ICP from 20 ± 11 to 13 ± 8 mm Hg (p < 0.001). In no patient who underwent hyperventilation therapy did SjvO2 fall below 55%. With induced hypertension, MABP in patients increased by 14 ± 5 mm Hg and ICP increased from 16 ± 9 to 19 ± 9 mm Hg (p = 0.001). With the aid of metabolic suppression, MABP remained stable and ICP decreased from 20 ± 10 to 16 ± 11 mm Hg (p < 0.001). A decrease in ICP of more than 20% below the baseline value was observed in 77.2, 5.5, and 48.8% of hyperventilation, induced-hypertension, and metabolic suppression tests, respectively (p < 0.001 for all comparisons). Predictors of an effective reduction in ICP included a high PaCO2 for hyperventilation, a high study GCS score for induced hypertension, and a high PaCO2 and a high CBF for metabolic suppression.

Conclusions Of the three modalities tested to reduce ICP, hyperventilation therapy was the most consistently effective, metabolic suppression therapy was variably effective, and induced hypertension was generally ineffective and in some instances significantly raised ICP. The results of this study suggest that hyperventilation may be used more aggressively to control ICP in head-injured patients, provided it is performed in conjunction with monitoring of SjvO2.

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Jens Conrad, Ali Ayyad, Christian Wüster, Wael Omran, Matthias M. Weber, Moritz A. Konerding, Wibke Müller-Forell, Alf Giese, and Joachim Oertel

OBJECTIVE

Over the past 2 decades, endoscopy has become an integral part of the surgical repertoire for skull base procedures. The present clinical evaluation and cadaver study compare binostril and mononostril endoscopic transnasal approaches and the surgical techniques involved.

METHODS

Forty patients with pituitary adenomas were treated with either binostril or mononostril endoscopic surgery. Neurosurgical, endocrinological, ophthalmological, and neuroradiological examinations were performed. Ten cadaver specimens were prepared, and surgical aspects of the preparation and neuroradiological examination were documented.

RESULTS

In the clinical evaluation, 0° optics were optimal in the nasal and sphenoidal phase of surgery for both techniques. For detection of tumor remnants, 30° optics were superior. The binostril approach was significantly more time consuming than the mononostril technique. The nasal retractor limited maneuverability of instruments during mononostril approaches in 5 of 20 patients. Endocrinological pituitary function, control of excessive hormone secretion, ophthalmological outcome, residual tumor, and rates of adverse events, such as CSF leaks and diabetes insipidus, were similar in both groups.

In the cadaver study, there was no significant difference in the time required for dissection via the binostril or mononostril technique. The panoramic view was superior in the binostril group; this was due to the possibility of wider opening of the sella in the craniocaudal and horizontal directions, but the need for removal of more of the nasal septum was disadvantageous.

CONCLUSIONS

Because of maneuverability of instruments and a wider view in the sphenoid sinus, the binostril technique is superior for resection of large tumors with parasellar and suprasellar expansion and tumors requiring extended approaches. The mononostril technique is preferable for tumors with limited extension in the intra- and suprasellar area.

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Matthias Oertel, W. John Boscardin, Walter D. Obrist, Thomas C. Glenn, David L. McArthur, Tooraj Gravori, Jae Hong Lee, and Neil A. Martin

Object. The purpose of this prospective study was to evaluate the cumulative incidence, duration, and time course of cerebral vasospasm after traumatic brain injury (TBI) in a cohort of 299 patients.

Methods. Transcranial Doppler (TCD) ultrasonography studies of blood flow velocity in the middle cerebral and basilar arteries (VMCA and VBA, respectively) were performed at regular intervals during the first 2 weeks posttrauma in association with 133Xe cerebral blood flow (CBF) measurements. According to current definitions of vasospasm, five different criteria were used to classify the patients: A (VMCA > 120 cm/second); B (VMCA > 120 cm/second and a Lindegaard ratio [LR] > 3); C (spasm index [SI] in the anterior circulation > 3.4); D (VBA > 90 cm/second); and E (SI in the posterior circulation > 2.5). Criteria C and E were considered to represent hemodynamically significant vasospasm. Mixed-effects spline models were used to analyze the data of multiple measurements with an inconsistent sampling rate.

Overall 45.2% of the patients demonstrated at least one criterion for vasospasm. The patients in whom vasospasm developed were significantly younger and had lower Glasgow Coma Scale scores on admission. The normalized cumulative incidences were 36.9 and 36.2% for patients with Criteria A and B, respectively. Hemodynamically significant vasospasm in the anterior circulation (Criterion C) was found in 44.6% of the patients, whereas vasospasm in the BA—Criterion D or E—was found in only 19 and 22.5% of the patients, respectively. The most common day of onset for Criteria A, B, D, and E was postinjury Day 2. The highest risk of developing hemodynamically significant vasospasm in the anterior circulation was found on Day 3. The daily prevalence of vasospasm in patients in the intensive care unit was 30% from postinjury Day 2 to Day 13. Vasospasm resolved after a duration of 5 days in 50% of the patients with Criterion A or B and after a period of 3.5 days in 50% of those patients with Criterion D or E. Hemodynamically significant vasospasm in the anterior circulation resolved after 2.5 days in 50% of the patients. The time course of that vasospasm was primarily determined by a decrease in CBF.

Conclusions. The incidence of vasospasm after TBI is similar to that following aneurysmal subarachnoid hemorrhage. Because vasospasm is a significant event in a high proportion of patients after severe head injury, close TCD and CBF monitoring is recommended for the treatment of such patients.

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Jae Hong Lee, Daniel F. Kelly, Matthias Oertel, David L. McArthur, Thomas C. Glenn, Paul Vespa, W. John Boscardin, and Neil A. Martin

Object. Contemporary management of head-injured patients is based on assumptions about CO2 reactivity, pressure autoregulation (PA), and vascular reactivity to pharmacological metabolic suppression. In this study, serial assessments of vasoreactivity of the middle cerebral artery (MCA) were performed using bilateral transcranial Doppler (TCD) ultrasonography.

Methods. Twenty-eight patients (mean age 33 ± 13 years, median Glasgow Coma Scale score of 7) underwent a total of 61 testing sessions during postinjury Days 0 to 13. The CO2 reactivity (58 studies in 28 patients), PA (51 studies in 23 patients), and metabolic suppression reactivity (35 studies in 16 patients) were quantified for each cerebral hemisphere by measuring changes in MCA velocity in response to transient hyperventilation, arterial blood pressure elevation, or propofol-induced burst suppression, respectively. One or both hemispheres registered below normal vasoreactivity scores in 40%, 69%, and 97% of study sessions for CO2 reactivity, PA, and metabolic suppression reactivity (p < 0.0001), respectively. Intracranial hypertension, classified as intracranial pressure (ICP) greater than 20 mm Hg at the time of testing, was associated with global impairment of CO2 reactivity, PA, and metabolic suppression reactivity (p < 0.05). A low baseline cerebral perfusion pressure (CPP) was also predictive of impaired CO2 reactivity and PA (p < 0.01). Early postinjury hypotension or hypoxia was also associated with impaired CO2 reactivity (p < 0.05), and hemorrhagic brain lesions in or overlying the MCA territory were predictive of impaired metabolic suppression reactivity (p < 0.01). The 6-month Glasgow Outcome Scale score correlated with the overall degree of impaired vasoreactivity (p < 0.05).

Conclusions. During the first 2 weeks after moderate or severe head injury, CO2 reactivity remains relatively intact, PA is variably impaired, and metabolic suppression reactivity remains severely impaired. Elevated ICP appears to affect all three components of vasoreactivity that were tested, whereas other clinical factors such as CPP, hypotensive and hypoxic insults, and hemorrhagic brain lesions have distinctly different impacts on the state of vasoreactivity. Incorporation of TCD ultrasonography—derived vasoreactivity data may facilitate more injury- and time-specific therapies for head-injured patients.

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