The impact of the reference imaging modality, registration method and intraoperative flat-panel computed tomography on the accuracy of the ROSA® stereotactic robot.

OBJECTIVE: To establish the impact of the imaging modality, registration method and use of intraoperative computed tomography (CT) scan on the accuracy of the ROSA® stereotactic robot. METHODS: Using a dedicated phantom device, we measured the accuracy of the stereotactic robot for 20 targets as a function of the registration method (frameless, FL, or frame-based, FB) and the reference imaging modality (3T magnetic resonance imaging, MRI, CT scanner or flat-panel CT, fpCT). We performed a retrospective study of the accuracy of the first 26 FB and 31 FL robotized stereotactic surgeries performed in our department. RESULTS: In a phantom study, the mean target accuracy was 1.59 mm for 3T MRI-guided FL surgery, 0.3 mm for fpCT-guided FL surgery and 0.3 mm for CT-guided FB surgery. In our retrospective series, the mean accuracy was 0.81 mm for FB stereotactic surgery, 1.22 mm for our 24 stereotactic surgery procedures with FL (surface recognition) registration and 0.7 mm for our 7 stereotactic surgery procedures with FL fiducial marker registration. Intraoperative fpCT fully corrected all the registration errors. CONCLUSIONS: The ROSA stereotactic robot is highly accurate. Robotized FB stereotactic surgery is more accurate than robotized FL stereotactic surgery.

Effect of surgery on periventricular white matter in normal pressure hydrocephalus patients: comparison of two methods of DTI analysis.

BACKGROUND: Diffusion tensor imaging (DTI) is a useful tool for assessing changes that occur in microstructures. We have developed a novel method for region of interest (ROI) delineation in the assessment of DTI parameters in patients with normal pressure hydrocephalus (NPH). PURPOSE: To compare the standard method and our novel method in an evaluation of the impact of surgery on periventricular white matter in patients with NPH. MATERIAL AND METHODS: Ten patients with NPH underwent 3T magnetic resonance imaging (MRI; including 12-direction DTI sequences) before and after surgery. We recorded diffusion parameters (λi, the fractional anisotropy [FA], the apparent diffusion coefficient, and Dr) in the internal capsule (IC) and the body of the corpus callosum (BCC). Using the standard delineation technique, regions of interest (ROIs) were positioned according to anatomical and functional considerations and then filled with several sub-ROIs. The ROIs delineated with our novel technique (extracted as the six sub-ROIs with the lowest standard deviation for the FA) were arranged in two rows (medial and lateral), from the ventricle to the brain surface. RESULTS: The within-ROI homogeneity was higher with the novel method than with the conventional method (P<10(-4)). When the conventional delineation method was applied to the IC data, only λ2 was found to be significantly greater after surgery; in contrast, application of our novel method evidenced a significant decrease in FA and λ1 and a significant increase in λ2 (P<0.05). Both before and after surgery, the FA in the medial row of ROIs was greater than the FA in the lateral row (P<0.01). In the BCC, only λ2 and Dr varied significantly (when evaluated with the novel method). CONCLUSION: Our results show that use of a novel method of DTI data analysis may be more sensitive to local changes induced by surgical procedures. Furthermore, this novel method was able to detect the transmantle pressure gradient related to the regional stress distribution.

Relationship between cerebrospinal fluid flow, ventricles morphology, and DTI properties in internal capsules: differences between Alzheimer's disease and normal-pressure hydrocephalus.

BACKGROUND: Normal-pressure hydrocephalus (NPH) and Alzheimer's disease (AD) have some similar clinical features and both involve white matter and cerebrospinal fluid (CSF) disorders. PURPOSE: To compare putative relationships between ventricular morphology, CSF flow, and white matter diffusion in AD and NPH. MATERIAL AND METHODS: Thirty patients (18 with AD and 12 with suspected NPH) were included in the study. All patients underwent a 3-Tesla MRI scan, which included phase-contrast MRI of the aqueduct (to assess the aqueductal CSF stroke volume) and a DTI session (to calculate the fractional anisotropy [FA] and apparent diffusion coefficient [ADC]) in the internal capsules). RESULTS: FA was correlated with ventricular volume in the suspected NPH population (P < 0.001; rs = 0.88), whereas the ADC was highly correlated with the aqueductal CSF stroke volume in AD (P < 0.001; rs = 0.79). CONCLUSION: Although AD and NPH both involve CSF disorders, the two diseases do not have the same impact on the internal capsules. The magnitude of the ADC is related to the aqueductal CSF stroke volume in AD, whereas FA is related to ventricular volume in NPH.

Bilateral abducens paralysis revealing bipartite spheno-occipital synchondrosis fracture in a child: case based update.

BACKGROUND: After reviewing the literature about sella turcica and spheno-occipital synchondrosis fracture, we present the case of a 6-year-old girl who suffered complex sphenoid bone fracture produced by an indirect mechanism. METHODS: The girl fell from her height after a blunt head injury due to a falling lamppost. RESULTS: Computer tomography (CT) scan showed occipital, sellar and clival fractures with pneumatocephalus. The probable fracture mechanism is contre-coup injury linked to osseous and brain oscillations after head trauma. CONCLUSION: Two complications, abducens nerve palsy and cerebrospinal fluid fistula, are observed and discussed.

Effect of transcranial magnetic stimulation on four types of pressure-programmable valves.

BACKGROUND: Exposure to powerful magnetic fields may alter the settings of programmable ventriculoperitoneal shunt valves or even cause permanent damage to these devices. Transcranial magnetic stimulation (TMS) and magnetic resonance imaging both generate a high-intensity, focal magnetic field. To the best of our knowledge, there is no literature data on the compatibility of TMS with neurosurgical implants. The aim of the present in vitro study was to investigate the effects of TMS on four types of pressure-programmable valves (the Strata 2 from Medtronic, the Polaris from Sophysa, the ProGAV from Miethke, and a cylindrical valve from Codman-Hakim). METHODS: We used a Magpro X100 stimulator (Medtronic) for monophasic or biphasic TMS via a circular or a figure-of-eight coil. Each valve setting was tested before and after exposure to TMS. Experiment 1: The effect of the coil-valve distance (10, 5, 2.5, and 1 cm) was assessed. Experiment 2: We mimicked in situ stimulation with a human mannequin by placing the valve in a retroauricular position, the TMS circular coil on the apex, and figure-of-eight coil centered over the primary motor area site. Temperature changes were monitored throughout the experiments. Experience 3: TMS-induced valve movements were assessed by using an in-house accelerometric setup. RESULTS: Our results primarily demonstrated that the Strata 2 and Codman-Hakim valves' settings were perturbed by TMS. There was no heating effect for any of the valves. However, TMS induced movements of the Strata 2, Polaris, and ProGAV valves. Experiment 1: The unsetting frequencies observed for the Strata 2 and the Codman-Hakim valve showed an influence of the distance, the coil model, and the magnetic field characteristics, whereas the Polaris and ProGAV's settings remained unchanged. Experiment 2: Unsetting occurred for Strata 2 valve with the circular coil only, whereas the Polaris, ProGAV, and Codman-Hakim valves' settings remained stable. Experiment 3: The Strata 2, Polaris, and ProGAV valves showed high-amplitude oscillations during TMS under all stimulation conditions, whereas the Codman-Hakim valve did not move. CONCLUSIONS: Our in vitro experiments showed that TMS can interfere with programmable shunt valves by inducing unsetting or movement. This finding suggests that great care must be taken if applying TMS in hydrocephalic, shunted patients.

Microsurgical anatomy of the medial tentorial artery of Bernasconi-Cassinari.

OBJECTIVE: In the current literature, there is a lack of detailed map of the origin, course and relationships of the medial tentorial artery (MTA) of Bernasconi-Cassinari often implicated in various diseases such as dural arteriovenous fistulas of the cranial base, stenotic lesions of the ICA, saccular infraclinoid intracavernous aneurysms and tentorial meningiomas. METHODS: Using a colored silicone mix preparation, ten cranial bases were examined using ×3 to ×40 magnification of the surgical microscope. RESULTS: The MTA arose as a single branch in 95% of cases from the MHT at the level of the C4 segment of the internal carotid artery. The average length of the MTA was 21.7 mm (range 20.0-23.4 mm). The average diameter of the MTA was 0.53 mm (range 0.49-0.60 mm).The MTA passed just below the lower dural ring detached from the lower margin of the anterior clinoid process. During its course, the MTA drop over the intracavernous segment of the abducens nerve twisted at its exit from the Dorello's canal and overlay the trochlear into the thickness of the free margin of the tentorium cerebelli. Vascular relationships of the MTA were venous trabeculation of the cavernous sinus, basilar plexus and branches of the inferolateral trunk. The MTA sent two terminal branches: one medial rectilinear, which pursued the initial dorsal course, and the other shorter with a lateral course, which disappeared into the lateral wall of the cavernous sinus. The medial branch of the MTA curved laterally, ramifying within the free edge of the tentorium cerebelli and anastomosing along the base of the dorsal part of the falx. CONCLUSION: The implications of these anatomic findings for surgery or endovascular procedure are reviewed and discussed.

Odontoid fracture complicating Jaffe-Lichtenstein disease. Case report.

The authors report the case of a 31-year-old man with polyostotic fibrous dysplasia who suffered a traumatic odontoid fracture in an area of a preexisting bone lesion. Conservative treatment was successfully performed. Jaffe-Lichtenstein disease is discussed along with differential diagnoses and alternative methods of treatment.

Urgent Anterior Cervical Osteophytectomy for an Asymptomatic Cervical Hyperostosis to Overcome Failed Intubation.

Cervical spondylosis and ankylosing hyperostosis of the cervical vertebrae are usually asymptomatic. This is a case report of a patient with massive anterior cervical osteophytes resulting in failure of intubation prior to a lumbar canal stenosis surgery. The osteophytes extended from C3 to C7 and resulted in the anterior displacement of the pharynx and the trachea. The patient was managed successfully with anterior cervical osteophytectomy.

Evaluation of Screw Placement Accuracy in Circumferential Lumbar Arthrodesis Using Robotic Assistance and Intraoperative Flat-Panel Computed Tomography.

BACKGROUND: Neuronavigation has become a common means of placing pedicle screws in vertebral arthrodesis, because it reduces the incidence of complications related to poor screw positioning. OBJECTIVE: The To evaluate the accuracy of pedicle screw placement during lumbar arthrodesis performed with the new ROSA Spine robot and intraoperative flat-panel computed tomography (fpCT) guidance. METHODS: We performed a descriptive, observational, retrospective, single-center study of patients having undergone transforaminal lumbar interbody fusion (TLIF) for degenerative pathologies with the ROSA Spine robot and intraoperative fpCT guidance. The primary endpoint was the presence or absence of pedicle wall breach, as assessed from the fpCT scan. Screw placement was graded according to Ravi's classification. RESULTS: Twenty-five patients were operated on between November 2014 and July 2016; 21 underwent minimally invasive TLIF, and 4 underwent open TLIF. The mean ± standard deviation operating time was 241 ± 49.8 minutes. Of the 110 screws placed, 101 (91.8%) were completely within the pedicle (Ravi grade A), 5 (4.5%) had a pedicle wall breach <2 mm (grade B), 2 (1.8%) had a pedicle wall breach of 2-4 mm (grade C), and 2 had pedicle wall breach >4 mm (grade D) (1.8%). One screw (a grade D) was replaced during surgery. None of the breaches were symptomatic. CONCLUSIONS: When coupled with fpCT, the ROSA Spine robot is a reliable, accurate means of performing lumbar pedicle screwing.

Frameless robotic stereotactic biopsies: a consecutive series of 100 cases.

OBJECT: Stereotactic biopsy procedures are an everyday part of neurosurgery. The procedure provides an accurate histological diagnosis with the least possible morbidity. Robotic stereotactic biopsy needs to be an accurate, safe, frameless, and rapid technique. This article reports the clinical results of a series of 100 frameless robotic biopsies using a Medtech ROSA device. METHODS: The authors retrospectively analyzed their first 100 frameless stereotactic biopsies performed with the robotic ROSA device: 84 biopsies were performed by frameless robotic surface registration, 7 were performed by robotic bone fiducial marker registration, and 9 were performed by scalp fiducial marker registration. Intraoperative flat-panel CT scanning was performed concomitantly in 25 cases. The operative details of the robotic biopsies, the diagnostic yield, and mortality and morbidity data observed in this series are reported. RESULTS: A histological diagnosis was established in 97 patients. No deaths or permanent morbidity related to surgery were observed. Six patients experienced transient neurological worsening. Six cases of bleeding within the lesion or along the biopsy trajectory were observed on postoperative CT scans but were associated with transient clinical symptoms in only 2 cases. Stereotactic surgery was performed with patients in the supine position in 93 cases and in the prone position in 7 cases. The use of fiducial markers was reserved for posterior fossa biopsy via a transcerebellar approach, via an occipital approach, or for pediatric biopsy. CONCLUSIONS: ROSA frameless stereotactic biopsies appear to be accurate and safe robotized frameless procedures.

Shunt revision for asymptomatic failure: surgical and clinical results.

OBJECTIVE: Shunt obstruction represents a permanent threat for patients with shunts, and its prevention and treatment are important parts of neurosurgeons' duties. Although there is little discussion regarding the need to reoperate for treatment of symptomatic shunt failure (SSF), the need to reoperate for treatment of asymptomatic shunt failure (ASF) is debated, as are the guidelines for the follow-up monitoring of patients with shunts. The goal of this study was to assess the effects of systematic follow-up monitoring and shunt revision for ASF; we reviewed our database to compare the results of shunt revision for ASF versus SSF. METHODS: We defined ASF as shunt failure diagnosed for an asymptomatic patient during a systematic consultation. In our institution, children who receive shunts for treatment of hydrocephalus are systematically monitored in an outpatient clinic, with clinical examinations and plain x-rays. Among 1,564 children with shunts, who were monitored for a mean of 10.7 years, 1106 (70.7%) required at least one shunt revision. The indication for the first revision was SSF in 609 cases and ASF in 305 cases; the indication was not specified in 192 cases. We studied the surgical outcomes after the first shunt revision and compared the results for SSF and ASF. RESULTS: After the first revision, shunt infections and subsequent shunt failure were significantly less frequent in the ASF group, compared with the SSF group. The interval between the first shunt revision and subsequent shunt failure was significantly longer in the ASF group. CONCLUSION: Our data support the practice of systematic follow-up monitoring for patients with shunts, for the early diagnosis and systematic treatment of ASF.

Estimation of the lateral ventricles volumes from a 2D image and its relationship with cerebrospinal fluid flow.

PURPOSE: This work suggests a fast estimation method of the lateral ventricles volume from a 2D image and then determines if this volume is correlated with the cerebrospinal fluid flow at the aqueductal and cerebral levels in neurodegenerative diseases. MATERIALS AND METHODS: Forty-five elderly patients suffering from Alzheimer's disease (19), normal pressure hydrocephalus (13), and vascular dementia (13) were involved and underwent anatomical and phase contrast MRI scans. Lateral ventricles and stroke volumes were assessed on anatomical and phase contrast scans, respectively. A common reference plane was used to calculate the lateral ventricles' area on 2D images. RESULTS: The largest volumes were observed in hydrocephalus patients. The linear regression between volumes and areas was computed, and a strong positive correlation was detected (R² = 0.9). A derived equation was determined to represent the volumes for any given area. On the other hand, no significant correlations were detected between ventricles and stroke volumes (R² ≤ 0.15). CONCLUSION: Lateral ventricles volumes are significantly proportional to the 2D reference section area and could be used for patients' follow-up even if 3D images are unavailable. The cerebrospinal fluid fluctuations in brain disorders may depend on many physiological parameters other than the ventricular morphology.

Cerebrospinal fluid and blood flow in mild cognitive impairment and Alzheimer's disease: a differential diagnosis from idiopathic normal pressure hydrocephalus.

BACKGROUND: Phase-contrast magnetic resonance imaging (PC-MRI) enables quantification of cerebrospinal fluid (CSF) flow and total cerebral blood (tCBF) flow and may be of value for the etiological diagnosis of neurodegenerative diseases. This investigation aimed to study CSF flow and intracerebral vascular flow in patients with Alzheimer's disease (AD) and patients with amnesic mild cognitive impairment (a-MCI) and to compare the results with patients with idiopathic normal pressure hydrocephalus (NPH) and with healthy elderly volunteers (HEV). METHODS: Ten a-MCI and 9 mild AD patients were identified in a comprehensive neurological and neuropsychological assessment. They underwent brain MRI; PC-MRI pulse sequence was performed with the following parameters: two views per segment; flip angle: 25° for vascular flow and 20° for CSF flow; field-of-view (FOV): 14 × 14 mm²; matrix: 256 × 128; slice thickness: 5 mm; with one excitation for exams on the 3 T machine, and 2 excitations for the 1.5 T machine exams. Velocity (encoding) sensitization was set to 80 cm/s for the vessels at the cervical level, 10 or 20 cm/s for the aqueduct and 5 cm/s for the cervical subarachnoid space (SAS). Dynamic flow images were analyzed with in-house processing software. The patients' results were compared with those obtained for HEVs (n = 12), and for NPH patients (n = 13), using multivariate analysis. RESULTS: Arterial tCBF and the calculated pulsatility index were significantly greater in a-MCI patients than in HEVs. In contrast, vascular parameters were lower in NPH patients. Cervical CSF flow analysis yielded similar values for all four populations. Aqueductal CSF stroke volumes (in µl per cardiac cycle) were similar in HEVs (34 ± 17) and AD patients (39 ± 18). In contrast, the aqueductal CSF was hyperdynamic in a-MCI patients (73 ± 33) and even more so in NPH patients (167 ± 89). CONCLUSION: Our preliminary data show that a-MCI patients present with high systolic arterial peak flows, which are associated with higher mean total cerebral arterial flows. Aqueductal CSF oscillations are within normal range in AD and higher than normal in NPH. This study provides an original dynamic vision of cerebral neurodegenerative diseases, consistent with the vascular theory for AD, and supporting primary flow disturbances different from those observed in NPH.

Spinal arachnoid cyst related to a nonaneurysmal perimesencephalic subarachnoid hemorrhage: case report.

OBJECTIVE AND IMPORTANCE: We report the first case of a delayed symptomatic spinal arachnoid cyst related to a nonaneurysmal perimesencephalic hemorrhage. We review the literature concerning posthemorrhagic spinal arachnoid cysts. CLINICAL PRESENTATION: A 64-year-old woman presented with progressive spinal cord compression symptoms 10 months after a nonaneurysmal perimesencephalic hemorrhage. Magnetic resonance imaging of the spine disclosed a dorsal and intradural cystic lesion producing posterior spinal cord compression. INTERVENTION: A thoracic laminectomy allowed complete resection of the cyst. Surgical and histological findings disclosed an intradural arachnoid cyst. On postoperative follow-up, spinal magnetic resonance imaging confirmed satisfactory decompression of the spinal cord. Because of extensive arachnoiditis, the patient experienced only partial recovery from neurological deficits. CONCLUSION: This extremely rare complication should be kept in mind when delayed lower-limb neurological deficits appear after subarachnoid hemorrhage, even in a perimesencephalic form.