Dilemmas and diagnostic difficulties in meningioma.

This article will review the uncommon locations and morphological features of meningiomas, which are important to recognize in order to avoid misdiagnosis. Uncommon locations will be demonstrated at the cerebellopontine angle, pineal, optic, intraventricular, and intradiploic regions. Unusual imaging features including cysts, metaplastic changes, and peritumoural oedema will also be discussed.

Sudden severe chest pain: thoracic dural arteriovenous fistula aneurysm rupture with intracranial subarachnoid haemorrhage.

Spinal perimedullary arteriovenous fistula (AVF) or dural arteriovenous fistula (DAVF) presenting as intracranial subarachnoid haemorrhage (SAH) is uncommon. A total of 16 cases have been reported to date. A majority of the reports described cervical spinal DAVF, while two other case reports described intracranial SAH secondary to lumbar and thoracic DAVF, respectively. We report a 61-year-old Chinese man with intracranial SAH secondary to thoracic DAVF aneurysm, who presented with sudden, severe chest pain, initially suggestive of aortic dissection/acute myocardial infarction. However, a careful examination of the history and physical signs, followed by appropriate and timely investigations enabled effective treatment to be administered promptly with a good outcome. This serves to illustrate the importance of investigating the entire cerebrospinal system when neurological symptoms and clinical signs suggest extracranial primary pathology.

Spinal epidural haemangioma associated with extensive gastrointestinal haemangiomas. A case report.

SUMMARY: A case of spinal epidural cavernous haemangioma associated with gastrointestinal haemangiomas is discussed. The patient was a young Chinese female presenting with chronic lower back pain. She had a history of extensive gastric and small bowel haemangiomas. Lumbar spine MRI showed a heterogeneously enhancing epidural mass infiltrating the paravertebral muscles. Open biopsy confirmed an epidural cavernous haemangioma. To our knowledge, an association between spinal epidural cavernous haemangiomas and gastrointestinal haemangiomas has not been reported.

Audit of diagnostic and interventional craniocervical catheter angiographic procedures at the Singapore General Hospital.

INTRODUCTION: Catheter angiography is an established imaging modality of evaluating cerebral and head and neck vascular diseases. It is, however, an invasive procedure with a small risk of complications. The aim of our study was to evaluate the prevalence of peri-procedural complications in a local hospital setting. MATERIALS AND METHODS: A total of 88 patients underwent diagnostic and interventional craniocervical procedures over 6 months in our department. The casenotes of 83 patients were retrospectively reviewed for complications arising from a total of 99 procedures carried out. RESULTS: A new focal neurological deficit developed in 3 different patients after a procedure, giving a prevalence of 3.0%. All these occurred in diagnostic procedures and were permanent deficits with correlative computed tomography (CT) or magnetic resonance (MR) imaging findings of acute cerebral infarction. All these occurred in high-risk patients who had severe underlying cerebrocarotid vascular compromise. There was 1 case of contrast medium-induced nephropathy (1.0%), occurring in a patient with pre-existing renal impairment. Local complications included 1 case of iatrogenic external iliac artery dissection (1.0%) and 5 cases (5.1%) of small and uncomplicated puncture site groin haematomas. CONCLUSION: The most significant complication associated with a craniocervical angiographic procedure was the development of post-procedural stroke in patients with significant preexisting cerebrocarotid vascular compromise. In the absence of this risk factor, craniocervical catheter angiography is a relatively safe procedure.

Diffusion weighted MR imaging in acute stroke: the SGH experience.

Cerebrovascular accident (CVA) is a leading cause of death and disability in many countries. Diffusion-weighted (DW) magnetic resonance (MR) imaging has been reported to be useful in the detection of acute strokes and as an investigative tool evaluating the therapeutic effects of neuroprotective and thrombolytic agents. The objectives of this study are to share our experience using the commercially available isotropic DW scan in imaging of acute stroke, assess its usefulness over conventional T2-weighted (T2W) scans in a busy clinical radiology unit and highlight it pitfalls. We found the rapid sub-minute DW technique well suited for ill and restless stroke patients and superior to T2W scans in many ways. It was highly sensitive to acute ischaemic lesions, made lesions easily identifiable and readily differentiated the acute lesion from a background of multiple chronic infarcts. However, there are potential pitfalls in the evaluation of small hyperacute posterior fossa strokes and venous infarcts. The major strength of this MR technique lies in its ability to diagnose hyperacute strokes and thence the potential for therapeutic thrombolysis, but unfortunately patients qualifying for the "therapeutic window" were a minority. More efforts need to be focused on public education in order for this powerful imaging modality to find its true value and contribute to viability of an effective thrombolytic programme.

Correlation of the apparent diffusion coefficient and the creatine level in early ischemic stroke: a comparison of different patterns by magnetic resonance.

It has been reported that reduction of the apparent diffusion coefficient (ADC) after stroke can persist for several days, after which the ADC increases gradually to an abnormally high level. We evaluated ADC values of stroke lesions and compared the results to the cellular density of the lesion by means of the creatine (Cre) level. This two-parameter estimation is of particular relevance in ascertaining the underlying cellular status. Lesion-to-contralateral ADC ratios (ADCn) were obtained based on diffusion-weighted echo-planar and fast spin-echo imaging. Single-voxel localized spectroscopy was used for quantification of cerebral metabolites in infarcted regions. Their levels were also compared to that in homotopic contralateral regions. Fifteen patients with ischemic stroke were examined at times ranging from 18-88 hours following the onset of symptoms. In the stroke lesion, there was a significant correlation between the ADC and the Cre level showing that the higher the cell density the lower the ADC value. For ADCn vs. the lesion Cre concentration and the lesion-to-contralateral Cre ratio (Cre(n)), the strengths of relationship were R2 = 0.70 and 0.58, respectively. It is concluded that ADC is a good reflection of cell density. Greatly lowered ADC values occur within the context of a stable cellularity. ADC and the Cre level have complementary roles in the characterization of stroke lesion with regard to the sequential stage.

Nipah viral encephalitis or Japanese encephalitis? MR findings in a new zoonotic disease.

BACKGROUND AND PURPOSE: An epidemic of suspected Japanese encephalitis occurred in Malaysia in 1998-1999 among pig farmers. In neighboring Singapore, an outbreak occurred among pig slaughterhouse workers. It was subsequently established that the causative agent in the outbreak was not the Japanese encephalitis virus but a previously unknown Hendra-like paramyxovirus named Nipah virus. METHODS: The brain MR images of eight patients with Nipah virus infection were reviewed. All patients tested negative for acute Japanese encephalitis virus. Seven patients had contrast-enhanced studies and six had diffusion-weighted examinations. RESULTS: All patients had multiple small bilateral foci of T2 prolongation within the subcortical and deep white matter. The periventricular region and corpus callosum were also involved. In addition to white matter disease, five patients had cortical lesions, three had brain stem involvement, and a single thalamic lesion was detected in one patient. All lesions were less than 1 cm in maximum diameter. In five patients, diffusion-weighted images showed increased signal. Four patients had leptomeningeal enhancement and four had enhancement of parenchymal lesions. CONCLUSION: The brain MR findings in patients infected with the newly discovered Nipah paramyxovirus are different from those of patients with Japanese encephalitis. In a zoonotic epidemic, this striking difference in the appearance and distribution of lesions is useful in differentiating these diseases. Diffusion-weighted imaging was advantageous in increasing lesion conspicuity.

Role of magnetic resonance imaging and magnetic resonance angiography in patients with hemifacial spasm.

Vascular compression of the facial nerve is a well recognized cause of hemifacial spasm (HFS). In this study, we described the magnetic resonance imaging (MRI) and three-dimensional magnetic resonance angiography (MRA) techniques used and findings in 34 patients with hemifacial spasm. A vascular abnormality, defined as a vessel seen in close proximity, touching or compressing the facial nerve, was identified in 22 of the 25 patients (88%) who had both MRI and MRA studies. Vessels identified were anterior inferior cerebellar artery (59.2%), posterior inferior cerebellar artery (13.6%), vertebral artery (18.2%) and basilar artery (4.5%). All vascular abnormalities were ipsilateral to the side of the HFS. Only 3 of the 12 controls (25%) had a vascular abnormality in both MRI and MRA studies. One of the 9 HFS patients (11.1%) who had MRI only had an ipsilateral vascular abnormality. There is a role for combined MRI and MRA studies in the non-invasive evaluation of patients with HFS.

Radiological features in a patient with Kimura's disease.

Kimura's disease is an immune mediated inflammatory disorder that usually involves the head and neck region, primarily affecting the salivary glands, adjacent muscle and regional lymph nodes. Peripheral blood eosinophilia is the norm. Clinically and radiologically, it is difficult to differentiate Kimura's disease from salivary gland malignancy, lymphoma or haemangioma. The radiological findings of a patient who presented with a left facial mass involving the left parotid gland and the adjacent muscles are discussed. We also propose that the difference in the degree of enhancement between the initial and subsequent computed tomography study done two and a half years later may be due to the development of increased fibrosis and sclerosis as the disease progresses.

Diagnosis of deep vein thrombosis by Duplex Doppler ultrasound imaging at the Singapore General Hospital.

Deep vein thrombosis (DVT) of the lower extremity is the major cause of pulmonary embolism and chronic venous obstruction disease of the legs. However, the clinical diagnosis of leg vein thrombosis is notoriously difficult. Venography, using iodine containing contrast materials, has been the most reliable older method for diagnosing thrombosis. It is relatively more invasive, requires exposure to radiation and is not free of risks. Doppler ultrasonography has been shown to be highly sensitive and specific in the diagnosis of obstruction of flow in veins. We present 25 patients studied at Singapore General Hospital (SGH) with Doppler for the presumptive clinical diagnosis of DVT. Thirteen were found to have complete or partial obstruction of leg veins and 12 showed normal veins. These 12 patients were thus spared the risk and expense of long term anticoagulation. In experienced hands, Duplex Doppler ultrasonograph is an excellent diagnostic modality for the diagnosis or exclusion of significant deep vein thrombosis of the legs. It can be carried out safely and reliably in the very sick, in patients with renal failure, diabetics and the pregnant.