Sami H. Erbay

Hypoglycemia and diffusion-weighted imaging

&NA; The effect of severe hypoglycemia on the brain is well known, ranging from alterations of mental status to profound coma and death. We describe a case of global diffusion abnormalities eventually resulting in death. This otherwise healthy patient presented with seizures and a serum glucose level less than 20 mg/dL. Testing suggested that the hypoglycemia was likely caused by exogenous insulin or perhaps insulin receptor antibodies. Magnetic resonance imaging on the day after admission showed regions of restricted diffusion in the temporal and occipital lobes as well as in the basal ganglia. Despite the large body of literature concerning the pathophysiology of hypoglycemia and its clinical implications, little is known regarding its radiologic correlations. Index Terms: hypoglycemia, diffusion, magnetic resonance imaging (MRI), seizure, metabolic disease

Magnetic Resonance Imaging of Intramedullary Spinal Cord Lesions: A Pictorial Review

Magnetic resonance imaging is the current imaging modality of choice in the evaluation of patients presenting with myelopathic symptoms in the search for spinal cord lesions. It is important for the radiologist to recognize and differentiate nonneoplastic from the neoplastic process of the spinal cord as the differentiation of the 2 entities is extremely crucial to the neurosurgeon. This article presents a broad spectrum of benign intramedullary spinal abnormalities including syrinx, contusion, abscess, infarction, myelitis, multiple sclerosis, sarcoid, cavernoma, and arteriovenous malformation. Rare intramedullary neoplasms including dermoid tumor, astrocytoma, ependymoma, hemangioblastoma, lymphoma, ganglioneuroblastoma, and metastases are also illustrated. The clinical presentation and magnetic resonance signal characteristics as well as the differential diagnosis of the intramedullary lesions are discussed. The potential pitfalls in the differentiation of tumors from nonneoplastic disease of the spinal cord are also elucidated.

Intracranial carotid artery calcification on head CT and its association with ischemic changes on brain MRI in patients presenting with stroke-like symptoms: retrospective analysis.

IntroductionOur purpose was to study the association between the intracranial arterial calcifications observed on head CT and brain infarcts demonstrated by MRI in patients presenting with acute stroke symptoms.MethodsInstitutional review board approval was obtained for this retrospective study which included 65 consecutive patients presenting acutely who had both head CT and MRI. Arterial calcifications of the vertebrobasilar system and the intracranial cavernous carotid arteries (intracranial carotid artery calcification, ICAC) were assigned a number (1 to 4) in the bone window images from CT scans. These four groups were then combined into high calcium (grades 3 and 4) and low calcium (grades 1 and 2) subgroups. Brain MRI was independently evaluated to identify acute and chronic large-vessel infarcts (LVI) and small-vessel infarcts (SVI). The relationship between ICAC and infarcts was evaluated before and after adjusting for demographics and cardiovascular risk factors.ResultsStatistical analysis could not be performed for the vertebrobasilar system due to an insufficient number of patients in the high calcium group. Of the 65 patients, 46 (71%) had a high ICAC grade on head CT. They were older and had a higher prevalence of cardiovascular risk factors. Acute SVI (P = 0.006), chronic SVI (P = 0.006) and acute LVI (P = 0.04) were associated with a high ICAC grade. After adjustment for age and other risk factors, only acute SVI was associated with a high ICAC grade (P = 0.002).ConclusionAlthough age emerged as the most important determinant of ischemic cerebral changes, there were rather complex interactions among multiple risk factors with different infarct types. A high ICAC grade demonstrated a correlation with acute SVI in our patients independent of these risk factors.

Association between neurovascular contact on MRI and response to gamma knife radiosurgery in trigeminal neuralgia.

Treatment with gamma knife radiosurgery (GKRS) provides adequate short-term pain control in about 70% of the patients with intractable trigeminal neuralgia (TN). The purpose of our study was to evaluate whether the presence of neurovascular contact (NVC) at the root entry zone of the trigeminal nerve on pre-gamma knife MR imaging predicts an increased likelihood of an adequate response to GKRS.We studied 40 consecutive patients who underwent GKRS for treatment of intractable TN. Two neuroradiologists blinded to the side of symptoms analyzed pre-treatment constructive interference in steady state (CISS) images to determine the presence of NVC by consensus. An adequate response was defined as freedom from pain with or without reduced need for medical therapy. Adequate short-term response to GKRS was seen in 29 (72.5%) of 40 patients. NVC was seen in 30 of the 40 patients. Twenty-five (83.3%) of 30 patients with NVC had adequate short-term response to GKRS. Only four (40%) of the 10 patients without NVC had adequate response to GKRS (X2=7.06; P<0.01). Patients with NVC were seven times more likely to have an adequate response to GKRS than those without NVC (odds ratio =7.5).The presence of NVC on pre-treatment MR imaging predicts an increased likelihood of an adequate response to GKRS.

Cough-Associated Headache in Patients with Chiari I Malformation: CSF Flow Analysis by Means of Cine Phase-Contrast MR Imaging

SUMMARY: The purpose of this study was to analyze the CSF flow in patients with Chiari I to determine differences between patients with and without CAH. Thirty patients with Chiari I malformation underwent cine-PC CSF flow imaging in the sagittal plane. CSF flow pulsations were analyzed by placing regions of interest in the anterior cervical subarachnoid space. Maximum CSF systolic (craniocaudal) and diastolic (caudocranial) velocities as well as the durations of CSF systole and diastole (measured in fractions of the cardiac cycle) were determined. In the region of interest just below the foramen magnum, patients with CAH had a significantly shorter CSF systole and longer diastole (P = .02). A CSF diastolic length of ≥0.75 of the cardiac cycle was 67% sensitive and 86% specific for CAH. Our results indicate that Cine-PC imaging can show differences in CSF flow patterns in patients with Chiari I with and without CAH.

Increased Cochlear Fluid-Attenuated Inversion Recovery Signal in Patients with Vestibular Schwannoma

BACKGROUND AND PURPOSE: Elevated protein levels have been reported in perilymph of patients with vestibular schwannoma. Fluid-attenuated inversion recovery (FLAIR) imaging is sensitive to high protein contents in fluids. The purpose of this study was to investigate if in patients with unilateral vestibular schwannoma, cochlear FLAIR signal intensity on the affected side is increased compared with the unaffected side and control subjects. Materials and METHODS: Fifteen patients with unilateral vestibular schwannoma and 25 age-matched control subjects (without a history of hearing loss) were retrospectively evaluated. All patients and controls had routine 5-mm FLAIR and T1- and T2-weighted imaging of the brain. The signal intensity of both cochleae was evaluated by placing a small region of interest on FLAIR images. The signal intensity of the brain stem was also determined by placing a second region of interest. A ratio of cochlear signal intensity to brain stem signal intensity (CIBI ratio) was determined. A t test was used to compare the CIBI ratios. RESULTS: In patients, the mean CIBI ratio of the affected side was 0.89 ± 0.18, and that of the unaffected side was 0.57 ± 0.12. In control subjects, it was 0.51 ± 0.07. The CIBI ratio of the affected side was significantly higher compared with the unaffected side (P < .001) and compared with control subjects (P < .001). CONCLUSION: Patients with vestibular schwannoma have increased cochlear FLAIR signal intensity on the affected side compared with the unaffected side and healthy subjects.

Application of Basic Principles of Physics to Head and Neck MR Angiography: Troubleshooting for Artifacts

Neurovascular imaging studies are routinely used for the assessment of headaches and changes in mental status, stroke workup, and evaluation of the arteriovenous structures of the head and neck. These imaging studies are being performed with greater frequency as the aging population continues to increase. Magnetic resonance (MR) angiographic imaging techniques are helpful in this setting. However, mastering these techniques requires an in-depth understanding of the basic principles of physics, complex flow patterns, and the correlation of MR angiographic findings with conventional MR imaging findings. More than one imaging technique may be used to solve difficult cases, with each technique contributing unique information. Unfortunately, incorporating findings obtained with multiple imaging modalities may add to the diagnostic challenge. To ensure diagnostic accuracy, it is essential that the radiologist carefully evaluate the details provided by these modalities in light of basic physics principles, the fundamentals of various imaging techniques, and common neurovascular imaging pitfalls.

Is Intracranial Atherosclerosis an Independent Risk Factor for Cerebral Atrophy? A Retrospective Evaluation

BackgroundOur purpose was to study the association between the intracranial atherosclerosis as measured by cavernous carotid artery calcification (ICAC) observed on head CT and atrophic changes of supra-tentorial brain demonstrated by MRI.MethodsInstitutional review board approval was obtained for this retrospective study incorporating 65 consecutive patients presenting acutely who had both head CT and MRI. Arterial calcifications of the intracranial cavernous carotids (ICAC) were assigned a number (1 to 4) in the bone window images from CT scans. These 4 groups were then combined into high (grades 3 and 4) and low calcium (grades 1 and 2) subgroups. Brain MRI was independently evaluated to identify cortical and central atrophy. Demographics and cardiovascular risk factors were evaluated in subjects with high and low ICAC. Relationship between CT demonstrated ICAC and brain atrophy patterns were evaluated both without and with adjustment for cerebral ischemic scores and cardiovascular risk factors.ResultsForty-six of the 65 (71%) patients had high ICAC on head CT. Subjects with high ICAC were older, and had higher prevalence of hypertension, diabetes, coronary artery disease (CAD), atrial fibrillation and history of previous stroke (CVA) compared to those with low ICAC. Age demonstrated strong correlation with both supratentorial atrophy patterns. There was no correlation between ICAC and cortical atrophy. There was correlation however between central atrophy and ICAC. This persisted even after adjustment for age.ConclusionAge is the most important determinant of atrophic cerebral changes. However, high ICAC demonstrated age independent association with central atrophy.

Sterile brain abscess due to juvenile xanthogranuloma: DWI characteristics.

Juvenile xanthogranuloma (JXG) is a disorder of non‐Langerhans cell histiocytosis that usually displays as a self‐limiting course in children. Rare systemic involvement implies poor prognosis. Although conventional and spectroscopic magnetic resonance imaging (MRI) findings of JXG in CNS have been described, diffusion imaging of intracranial JXG has not been reported. Our case report is the first manuscript to describe diffusion restriction of a cerebral lesion seen in the setting of JXG. Since diffusion restriction has not been described in the setting of JXG but it is more commonly associated with infectious cerebral abscess, this finding has had significant impact in the management. Central nervous system (CNS) lesion of our patient has also had additional imaging features similar to typical infectious cerebral abscess. Extensive work‐up has been unrevealing any infectious source. Patient has had biopsy proven peripheral sterile abscesses. After extensive discussion with the family, brain biopsy is deferred. Intravenous steroid therapy is initiated in intensive care setting. All of the lesions have gradually responded to steroid therapy. CNS lesion has taken the longest time to clear.

Prospective Evaluation of the Role of Atherosclerosis on Cerebral Atrophy: Pilot Study

Our purpose was to study the association between atherosclerosis measured by arterial calcium on computed tomography (CT) and cerebral atrophy demonstrated by brain magnetic resonance imaging (MRI).