Igor Paredes

Basic Principles of Hemodynamics and Cerebral Aneurysms.

BACKGROUND Rupture is the most serious consequence of cerebral aneurysms, and its likelihood depends on nonmodifiable and modifiable risk factors. Recent efforts have focused on analyzing the effects of hemodynamic forces on the initiation, growth, and rupture of cerebral aneurysms. Studies of the role of hemodynamics in the physiopathology of intracranial aneurysms fall between mechanical engineering and molecular biology. METHODS This review summarizes the basic principles of the effect of hemodynamic forces on the cerebral vascular wall. CONCLUSIONS The size of the aneurysm dome is the most common parameter used in clinical practice to estimate the risk of rupture. However, relying only on aneurysm size means excessively simplifying a more complicated reality. Aneurysms emerge in areas of the vascular wall exposed to high wall shear stress. The direction in which blood flows once an aneurysm forms depends on aspects such as neck diameter, its angle with respect to the parent artery, the parent vessel caliber, the caliber or the angle of efferent vessels, and aneurysm shape. The progression and rupture of aneurysms have been associated with zones of the aneurysm wall exposed to both high and low wall shear stresses. Advances in this challenging and growing field are intended to predict more precisely the risk of rupture of aneurysms and to better understand the mechanisms of origin and growth of aneurysms.

Cranioplasty after decompressive craniectomy. A prospective series analyzing complications and clinical improvement.

BACKGROUND Cranioplasty is carried out for cosmetic reasons and for protection, but it may also lead to some neurological improvement after the bone flap placement. Complications of cranioplasty are more frequent than expected for a scheduled neurosurgical procedure. We tried to identify factors associated with both complications and improvement after cranioplasty. METHODS We prospectively studied the cranioplasties performed in our hospital from November 2009 to November 2013. Patients whose initial reason for bone removal was tumor infiltration were excluded. Demographic, clinical and radiological data were collected. The NIH Stroke Scale and Barthel Self-Care Index scores were obtained both before and within 72 h after cranioplasty. The outcome measures were the occurrences of complications and clinical improvement. RESULTS Fifty-five cranioplasties were performed. The material used for the cranioplasty was autologous bone in 42 cases, polyetheretherketone (PEEK) in 7 and methacrylate in 6. The average size of the bone defect was 69.5 (19.5-149.5) cm2. The time elapsed between decompressive craniectomy and cranioplasty was 309 (25-1217) days. There were 10 complications (7 severe and 3 mild), an 18.2% complication rate. Statistically significant risk factors of complications were identified as a Barthel≤70 (Odds ratio [OR] 22; 2.5-192; P=0.005), age over 45 years (OR 13.5; 1.5-115; P=0.01) and early surgery (≤85 days; OR 8; 1.69-37.03, P=0.004). After multivariate analysis, Barthel≤70 and age over 45 years remained independent predictors of complications. Twenty-two (40%) of the 55 patients showed objective improvement. Early surgery (<85 days) increased the likelihood of improvement (OR 4.67; 1.05-20.83; P=0.035). Larger bone defects seemed to be related with improvement, but differences in defect size were not statistically significant (75.3 vs 65.6 cm2; P=0.1). CONCLUSIONS The complication rate of cranioplasty is higher than for other elective neurosurgical procedures. Older age, poorer functional situation (worse Barthel index score) and early surgery (≤85 days) are independent risk factors for complications. However, cranioplasty produces clinical benefits beyond protection and esthetic improvement. Earlier surgery and larger bone defects seem to increase the likelihood of clinical improvement.

A severe case of Hirayama disease successfully treated by anterior cervical fusion

Hirayama disease, or juvenile amyotrophy of distal upper extremity, is a benign, self-limiting cervical myelopathy consisting of selective unilateral weakness of the hand and forearm. The weakness slowly progresses until spontaneous arrest occurs within 5 years of onset. The condition predominantly affects Asian males and is thought to be secondary to spinal cord compression during neck flexion, because of a forward displacement of the posterior dural sac. The authors present what is to their knowledge the first reported case of a Caucasian male with a severe form of Hirayama disease, suffering from weakness of the leg as well as the forearm. An abnormal range of cervical flexion was observed at the C5-6 level. The patient was successfully treated by anterior cervical discectomy and fusion.

Acute neurological deterioration as a result of two synchronous hemorrhagic spinal ependymomas

Background: Ependymomas are the most common intramedullary tumors in adults and are the most common in mid-adult years. The presence of synchronous ependymomas in different sites of the spine is not common and it is even more infrequent to find hemorrhage from a spinal ependymoma as a cause of neurological deterioration. Case Description: A 32-year-old man presented with back pain and progressive paraparesia. Magnetic resonance (MR) showed two intradural extramedullary lesions on spinal canal with signs of acute hemorrhage. The patient underwent emergent surgical decompression and resection. Pathology revealed myxopapillary ependymomas. Conclusion: To our knowledge, we report the first case of a patient with acute neurological deterioration as a consequence of synchronous bleeding of two spinal ependymomas located at different levels in the spinal cord. This study illustrates the importance of recognizing the rare, but known occurrence of acute neurological deterioration after spontaneous hemorrhage in spinal ependymomas.

Dorsal myelopathy secondary to epidural fibrous scar tissue around a spinal cord stimulation electrode.

The authors describe a patient with delayed thoracic spinal cord compression due to fibrous scar tissue around an epidural electrode used in spinal cord stimulation (SCS). One year after implantation of the system the stimulation became ineffective, and 1 year later the patient developed progressive paraparesis. There was no evidence of device-related complications on plain radiographs and CT scans, so the system was removed to perform MRI studies. These studies showed a dorsal myelopathy secondary to scar tissue around the electrode. At surgery thick scar tissue was resected, and the patients neurological symptoms improved. The histological examination confirmed fibrosis, and microbiological studies excluded chronic infection. As far as the authors are aware, this complication has never been reported before at the thoracic level. Scarring around SCS electrodes should be considered as a late complication and as a possible cause of the tolerance phenomenon.

Cervical Spinal Cord Injury without Computed Tomography Evidence of Trauma in Adults: Magnetic Resonance Imaging Prognostic Factors

BACKGROUND Spinal cord injury (SCI) without computed tomography evidence of trauma is underreported in adults and is considered a subtype of SCI with relatively good outcome. Despite this, few studies have been performed to determine specific imaging-related prognostic factors. Our objective is to describe the imaging characteristics of patients experiencing blunt cervical spine trauma with neurologic deficits, but without radiologic abnormalities and associated prognostic factors. METHODS A retrospective review of all adult patients with cervical SCI admitted to the emergency room of 2 university hospitals from January 2004 to December 2013 was performed. Only patients with a magnetic resonance imaging (MRI) performed within 72 hours after trauma were included for further analysis. All patients with bony injury or traumatic malalignment were excluded. Data gathered on the remaining patients included demographics, mechanism of injury, severity of SCI, long-term patient outcome, improvement in neurologic condition, and MRI results. RESULTS There were 48 patients who met the inclusion and exclusion criteria, and 40 who demonstrated improvement in the neurologic examination at follow-up. Disruption of either the anterior longitudinal ligament or ligamentum flavum and larger lesions in the MRI were predictors of lack of neurologic improvement. CONCLUSIONS Early MRI has prognostic value in patients suffering SCI without computed tomography evidence of trauma. Lesion length is a powerful predictor of outcome in this subgroup of patients. Soft tissue injury plays a role in the severity of injury and the ability to recover in this subgroups of patients.

Contrecoup Traumatic Intracerebral Hemorrhage: A Geometric Study of the Impact Site and Association with Hemorrhagic Progression

Traumatic intracerebral hemorrhage (TICH) represents 13-48% of the lesions after a traumatic brain injury (TBI). The frequency of TICH-hemorrhagic progression (TICH-HP) is estimated to be approximately 38-63%. The relationship between the impact site and TICH location has been described in many autopsy-based series. This association, however, has not been consistently demonstrated since the introduction of computed tomography (CT) for studying TBI. This study aimed to determine the association between the impact site and TICH location in patients with moderate and severe TBI. We also analyzed the associations between the TICH location, the impact site, the production mechanism (coup or contrecoup), and hemorrhagic progression. We retrospectively analyzed the records of 408 patients after a moderate or severe TBI between January 2010 and November 2014. We identified 177 patients with a total of 369 TICHs. We found a statistically significant association between frontal TICHs and impact sites located on the anterior area of the head (OR 5.8, p < 0.001). The temporal TICH location was significantly associated with impact sites located on the posterior head area (OR 4.9, p < 0.001). Anterior and lateral TICHs were associated with impact sites located at less than 90 degrees (coup) (OR 1.64, p = 0.03) and more than 90 degrees (contrecoup), respectively. Factors independently associated with TICH-HP obtained through logistic regression included an initial volume of <1 cc, cisternal compression, falls, acute subdural hematoma, multiple TICHs, and contrecoup TICHs. We demonstrated a significant association between the TICH location and impact site. The contrecoup represents a risk factor independently associated with hemorrhagic progression.

Spinal Cord Injury after Blunt Cervical Spine Trauma: Correlation of Soft-Tissue Damage and Extension of Lesion

This study retrospectively evaluates whether ligamentous injury or disk disruption after spinal cord injury correlates with lesion length. Length of lesion, disk disruption, ligamentous injury association, and extent of spinal cord injury were statistically assessed. The number of ligaments affected had a positive correlation with the extension of the lesion. Thus, in cervical spine trauma, a specific pattern of ligamentous injury correlates with the length of the spinal cord lesion. BACKGROUND AND PURPOSE: In patients with spinal cord injury after blunt trauma, several studies have observed a correlation between neurologic impairment and radiologic findings. Few studies have been performed to correlate spinal cord injury with ligamentous injury. The purpose of this study was to retrospectively evaluate whether ligamentous injury or disk disruption after spinal cord injury correlates with lesion length. MATERIALS AND METHODS: We retrospectively reviewed 108 patients diagnosed with traumatic spinal cord injury after cervical trauma between 1990–2011. Plain films, CT, and MR imaging were performed on patients and then reviewed for this study. MR imaging was performed within 96 hours after cervical trauma for all patients. Data regarding ligamentous injury, disk injury, and the extent of the spinal cord injury were collected from an adequate number of MR images. We evaluated anterior longitudinal ligaments, posterior longitudinal ligaments, and the ligamentum flavum. Length of lesion, disk disruption, and ligamentous injury association, as well as the extent of the spinal cord injury were statistically assessed by means of univariate analysis, with the use of nonparametric tests and multivariate analysis along with linear regression. RESULTS: There were significant differences in lesion length on T2-weighted images for anterior longitudinal ligaments, posterior longitudinal ligaments, and ligamentum flavum in the univariate analysis; however, when this was adjusted by age, level of injury, sex, and disruption of the soft tissue evaluated (disk, anterior longitudinal ligaments, posterior longitudinal ligaments, and ligamentum flavum) in a multivariable analysis, only ligamentum flavum showed a statistically significant association with lesion length. Furthermore, the number of ligaments affected had a positive correlation with the extension of the lesion. CONCLUSIONS: In cervical spine trauma, a specific pattern of ligamentous injury correlates with the length of the spinal cord lesion in MR imaging studies. Ligamentous injury detected by MR imaging is not a dynamic finding; thus it proved to be useful in predicting neurologic outcome in patients for whom the MR imaging examination was delayed.

Normal pressure subdural hygroma with mass effect as a complication of decompressive craniectomy

Background: Subdural posttraumatic collections are called usually Traumatic Subdural Hygroma (TSH). TSH is an accumulation of cerebrospinal fluid (CSF) in the subdural space after head injury. These collections have also been called Traumatic Subdural Effusion (TSE) or External Hydrocephalous (EHP) according to liquid composition, or image features. There is no agreement about the pathogenesis of these entities, how to define them or if they are even different phenomena at all. Case Description: We present a case of a complex posttraumatic subdural collection, the role of cranioplasty as definite solution and review the literature related to this complication. Conclusion: Patients who undergo decompressive craniectomy (DC) have a risk of suffering a subdural collection of 21-50%. Few of these collections will become symptomatic and will need evacuation. When this happens, cranioplasty might be the definitive solution.

The Effect of Cranioplasty on Cerebral Hemodynamics as Measured by Perfusion Computed Tomography and Doppler Ultrasonography

Cranioplasties are performed to protect the brain and correct cosmetic defects, but there is growing evidence that this procedure may result in neurological improvement. We prospectively studied cranioplasties performed at our hospital over a 5-year period. The National Institute of Health Stroke Scale and Barthel index were recorded prior to and within 72 h after the cranioplasty. A perfusion computed tomography (PCT) and transcranial Doppler sonography (TCDS) were performed prior to and 72 h after the surgery. For the PCT, regions irrigated by the anterior cerebral artery, the middle cerebral artery (MCA), the posterior cerebral artery, and the basal ganglia were selected, as well as the mean values for the hemisphere. The sonography was performed in the sitting and the supine position for the MCA and internal carotid. The velocities, pulsatility index, resistance index, and Lindegaard ratio (LR) were obtained, as well as a variation value for the LR (ΔLR = LR sitting - LR supine). Fifty-four patients were included in the study. Of these, 23 (42.6%) patients presented with objective improvement. The mean cerebral blood flow of the defective side (m-CBF-d) increased from 101.86 to 117.17 mL/100 g/min (p = 0.064), and the m-CBF of the healthy side (m-CBF-h) increased from 128.14 to 145.73 mL/100 g/min (p = 0.028). With regard to the TCDS, the ΔLR was greater on the defective side prior the surgery in those patients who showed improvement (1.295 vs. -0.714; p = 0.002). Cranioplasty resulted in clinical improvement in 40% of the patients, with an increase in the post-surgical CBF. The larger variations in the LR when the patient is moved from the sitting to the supine position might predict the clinical improvement.