Matthew T. Walker

Quantitative cerebral perfusion using dynamic susceptibility contrast MRI: Evaluation of reproducibility and age- and gender-dependence with fully automatic image postprocessing algorithm

A novel approach for quantifying cerebral blood flow (CBF) is proposed that combines the bookend technique of calculating cerebral perfusion with an automatic postprocessing algorithm. The reproducibility of the quantitative CBF (qCBF) measurement in healthy controls (N = 8) showed a higher intraclass correlation coefficient (ICC) and lower coefficient of variation (COV) when calculated with automatic analysis (ICC/COV = 0.90/0.09) than when compared to conventional manual analysis (ICC/COV = 0.58/0.19). Also, the reproducibility in patients (N = 25) was successfully evaluated with the automatic analysis (ICC/COV = 0.81/0.14). In 175 consecutive clinical scans, we found 3.0% and 7.4% of qCBF decrease per decade in white matter (WM) (21.5 ± 6.66 ml/100 g‐min) and gray matter (GM) (49.6 ± 16.2 ml/100 g‐min), respectively. Cerebral blood volume (CBV) showed a significant 3.7% decrease per decade in GM (3.00 ± 0.94 ml/100 g) but not in WM (1.69 ± 0.40 ml/100 g). Mean transit time (MTT) increased by 1.9% and 3.8% per decade in WM (5.04 ± 0.88 s) and GM (4.14 ± 0.80 s), respectively. qCBF and MTT values between males (N = 85) and females (N = 90) were significantly different in GM. Women showed 11% higher qCBF as well as a higher decrease in qCBF with increasing age than men in the whole brain (WB). Our results supported the notion that population average empirical quantification of cerebral perfusion is subject to individual variation as well as age‐ and gender‐dependent variability. Magn Reson Med, 2007.

Repetitive transcranial magnetic stimulation-associated neurobehavioral gains during coma recovery

BACKGROUND Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive method to induce changes in cortical neural excitability. This report presents findings from the first participant of a safety and efficacy study that examined a therapeutic rTMS protocol for persons with severe traumatic brain injury (TBI). OBJECTIVE The primary hypothesis was that there will be no adverse events related to the provision of a 6-week rTMS protocol for persons with severe TBI who remain, at best, in a minimally conscious state for longer than 3 months. The secondary hypothesis was that the rTMS protocol would induce significant neurobehavioral gains during treatment and that these gains would persist at 6-week follow-up. METHODS A 6-week rTMS protocol (30 sessions) was delivered to a 26-year-old man who remained in a vegetative state 287 days after severe TBI. Stimulation was directed over the right dorsolateral prefrontal cortex. Repeated safety measures, neurobehavioral assessments, clinical examinations, and evoked potentials (EP) were obtained at baseline, every fifth rTMS session (weekly), and at a 6-week follow-up. RESULTS There were no adverse events related to the provision of rTMS treatment. A trend toward significant (P = .066) neurobehavioral gains was temporally related to provision of rTMS. Left-sided brain stem auditory EP wave V latencies and waves I to V interpeak latencies improved along with neurobehavioral gains during provision of rTMS, suggesting that improved neural conduction in the pathway mediated the neurobehavioral improvements. CONCLUSIONS Repetitive TMS merits further investigation as a safe therapeutic intervention to alter neural activity, to modulate neural activity, and/or to facilitate recovery in persons with disordered consciousness subsequent to severe TBI.

Distinction between paraclinoid and cavernous sinus aneurysms with computed tomographic angiography.

OBJECTIVETo examine the reliability of using the optic strut as a landmark in computed tomographic (CT) angiography, to differentiate between intradural and extradural (cavernous sinus) aneurysms involving the paraclinoid segment of the internal carotid artery (ICA). METHODSMicroanatomic dissections were performed with five cadaveric heads (10 sides), to establish the relationships of the optic strut to the cavernous sinus and the ICA. Results from these anatomic studies were compared with intraoperative and CT angiographic findings for four patients with nine intracranial aneurysms involving the paraclinoid segment of the ICA. RESULTSThe inferior boundary of the optic strut accurately localized the point at which the ICA pierced the oculomotor membrane (proximal dural ring) and exited the cavernous sinus. The optic strut and its relationship to the ICA could be well observed on CT angiograms. During surgery, six of six aneurysms that arose distal to the optic strut were identified intradurally and were successfully clipped. Conversely, all aneurysms that arose proximal to the optic strut were observed to lie within the cavernous sinus. An aneurysm at the optic strut was within the clinoid segment or interdural, between the proximal and distal rings. CONCLUSIONThe optic strut, as identified with CT angiography, provided a reliable anatomic landmark for accurate discrimination between intradural and extradural (cavernous sinus) aneurysms.

Bing–Neel syndrome: an illustrative case and a comprehensive review of the published literature

Waldenstrom’s macroglobulinemia (WM) is a chronic lymphoproliferative disorder within the spectrum of lymphoplasmacytic lymphoma characterized by proliferation of plasma cells, small lymphocytes, and plasmacytoid lymphocytes. Central nervous system involvement is very rare (Bing–Neel [BN] syndrome). We present the case of a 62-year-old woman previously diagnosed with WM who presented with Bing–Neel syndrome and review the published literature which consists of only case reports. We performed a Medline search using the terms “Waldenstrom’s macroglobulinemia and central nervous system” and “Bing–Neel” collecting data on presentation, evaluation, treatment, and outcome and summarizing these findings in the largest pooled series to date. Central nervous system manifestations are localization related. Serum laboratory testing reflects systemic disease. Cerebrospinal fluid analysis may show lymphocytic pleocytosis, elevated protein, and IgM kappa or lambda light chain restriction; cytology results are variable. Imaging is frequently abnormal. Biopsy confirms the diagnosis. Treatment data are limited, but responses are seen with radiation and/or chemotherapy. BN syndrome is a very rare complication of WM that should be considered in patients with neurologic symptoms and a history of WM. Treatment should be initiated as responses do occur that may improve quality of life and extend it when limited or no active systemic disease is present.

Lumbosacral cerebrospinal fluid volume in humans using three-dimensional magnetic resonance imaging.

BACKGROUND: The clinical response to spinal anesthesia is influenced by lumbosacral cerebrospinal fluid (CSF) volume, which is highly variable among patients. METHODS: Lumbosacral magnetic resonance images were obtained in 71 patients using a long echo time (TE = 198 msec), fast spin echo sequence with fat suppression. Three-dimensional images were created and lumbosacral CSF volume was estimated using a threshold-based region growing algorithm. RESULTS: A validation experiment using a water bath and cadaveric spinal cord demonstrated that the technique was accurate (1.4 ± 0.4% difference between estimated and measured). The coefficient of variance was 0.42% among the three estimated CSF values per subject. The mean calculated volume was 35.8 ± 10.9 mL with a range of 10.6-61.3 mL. Lumbosacral CSF volume was widely variable among patients and was inversely proportional to body mass index (r = −.276, P = 0.02). Mean calculated lumbosacral CSF volumes were smaller in the group of subjects that had radiographic diagnoses of spinal stenosis when compared with subjects with no diagnosis (mean difference −8.4 mL, 95% CI of the difference, −16.1 to −0.8 mL, P = 0.03) and were not different when compared with those with herniated disk disease (mean difference −6.4 mL, 95% CI of the difference −14.7 to 1.9 mL, P = 0.19). CONCLUSIONS: Application of this technique to clinical investigations may further enhance our understanding of spinal anesthesia.

Persistent trigeminal artery terminating in the posterior inferior cerebellar artery: case report.

OBJECTIVEPersistent trigeminal arteries are rare and represent a remnant of the fetal carotid-basilar circulation. They typically extend from the internal carotid artery to the basilar artery. An unusual case of a patient with a trigeminal artery originating from the internal carotid artery and terminating as the dominant hemispheric branch of the posterior inferior cerebellar artery is presented. CLINICAL PRESENTATIONA 66-year-old woman presented to the emergency department with pulsatile tinnitus, increasing left eye pain, proptosis, conjunctival injection, diplopia, and decreased visual acuity. Conventional contrast-enhanced computed tomographic and magnetic resonance imaging demonstrated findings consistent with a left carotid-cavernous fistula. The patient underwent an emergency diagnostic cerebral angiogram. Besides an indirect carotid-cavernous fistula on the left side, a right-sided persistent trigeminal artery terminating as the dominant hemispheric trunk of the posteroinferior cerebellar artery was incidentally noted. The vermian branch of the right posteroinferior cerebellar artery arose from the ipsilateral vertebral artery, whereas duplicate superior cerebellar arteries supplied the left posteroinferior cerebellar artery region. INTERVENTIONThe patient was treated for the indirect carotid-cavernous fistula with detachable platinum coils and N-butyl cyanoacrylate, resulting in the resolution of her symptoms. CONCLUSIONWe report a case of a persistent trigeminal artery supplying only the cerebellar hemisphere. The clinical significance of this anomaly relates to its role in endovascular therapeutic and surgical complications and the paradoxical lesions in the cerebellum that occur as a result of carotid disease. We also discuss the Saltzman classification of persistent trigeminal arteries and their variants.

Imaging Modalities in Mild Traumatic Brain Injury and Sports Concussion

Mild traumatic brain injury is a significant public health issue that has been gaining considerable attention over the past few years. After injury, a large percentage of patients experience postconcussive symptoms that affect work and school performance and that carry significant medicolegal implications. Conventional imaging modalities (computed tomography and magnetic resonance imaging) are insensitive to microstructural changes and underestimate the degree of diffuse axonal injury and metabolic changes. Newer imaging techniques have attempted to better diagnose and characterize diffuse axonal injury and the metabolic and functional aspects of traumatic brain injury. The following review article summarizes the currently available imaging studies and describes the novel and more investigational techniques available for mild traumatic brain injury. A suggested algorithm is offered.

Advanced noninvasive imaging of spinal vascular malformations.

Spinal vascular malformations (SVMs) are an uncommon, heterogeneous group of vascular anomalies that can render devastating neurological consequences if they are not diagnosed and treated in a timely fashion. Imaging SVMs has always presented a formidable challenge because their clinical and imaging presentations resemble those of neoplasms, demyelination diseases, and infection. Advancements in noninvasive imaging modalities (MR and CT angiography) have increased during the last decade and have improved the ability to accurately diagnose spinal vascular anomalies. In addition, intraoperative imaging techniques have been developed that aid in the intraoperative assessment before, during, and after resection of these lesions with minimal and/or optimal use of spinal digital subtraction angiography. In this report, the authors review recent advancements in the imaging of SVMs that will likely lead to more timely diagnoses and treatment while reducing procedural risk exposure to the patients who harbor these uncommon spinal lesions.

4D radial contrast-enhanced MR angiography with sliding subtraction

A method is presented for high spatial and temporal resolution 3D contrast‐enhanced magnetic resonance angiography. The overall technique involves a set of interrelated components suited to high‐frame‐rate angiography, including 3D cylindrical k‐space sampling, angular undersampling, asymmetric sampling, sliding window reconstruction, pseudorandom view ordering, and a sliding subtraction mask. Computer simulations and volunteer studies demonstrated the utility of each component of the technique. Angiograms of one hemisphere of the intracranial vasculature were acquired with a pixel size of 1.1 × 1.1 × 2.8 mm and a frame rate of 0.35 sec based on a temporal resolution of 3.5 sec. Such a 3D time‐resolved, or “4D,” technique has the potential to noninvasively acquire diagnostic quality images of certain anatomic regions with a frame rate fast enough to not only ensure the capture of an uncontaminated arterial phase, but even demonstrate contrast bolus flow dynamics. Clinical applications include noninvasive imaging of arteriovenous shunting, which is demonstrated with a patient study. Magn Reson Med 58:962–972, 2007.

Central and peripheral fusiform aneurysms six years after left atrial myxoma resection

Central nervous system embolisation of left atrial myxoma is well documented.1 The most common neurological sequel is acute cerebral ischaemia secondary to vessel occlusion by tumour.2 Delayed neurological complications are much less common and may result from tumour recurrence with embolisation, progressive vascular stenosis, aneurysm formation with subsequent rupture, or parenchymal metastasis.2 We report the occurrence of multiple myxomatous aneurysms in a patient six years after resection of a left atrial myxoma who was experiencing transient ischaemic attacks in the same distribution as the largest aneurysms. These lesions included bilateral fusiform aneurysms of the superior cerebellar and posterior cerebral arteries. A 60 year old woman had a two week history of progressive occipital headache, intermittent visual changes, right facial pain, and imbalance. On examination, she had mild left upper and lower extremity weakness and mild cerebellar asymmetry. The patient reported a history of left atrial myxoma resection six years before presentation. Atherosclerotic risk factors included remote tobacco use and raised serum cholesterol. Pertinent drug treatment included fluvastatin and clopidogrel. Magnetic resonance imaging (MRI) of the brain suggested aneurysms of the superior cerebellar arteries or posterior cerebral arteries. The MRI also revealed areas of previous infarction in multiple vascular distributions including the left superior cerebellar artery and both posterior cerebral arteries. Digital subtraction angiography showed large irregular fusiform aneurysms of the proximal superior cerebellar arteries (fig …