Magnetic resonance imaging in central nervous system sarcoidosis.

We performed brain MRIs on 21 patients with CNS sarcoidosis. Brain CTs were performed in 18 of these. Parenchymal lesions were seen in 17 of 21 with MRI, compared with 9 of 18 with CT. MRI detected a greater number of parenchymal lesions in cases where both CT and MRI were positive, and some lesions appeared more extensive with MRI than with CT. The most common MRI pattern was one of periventricular and multifocal white matter lesions (14 cases). Such a pattern is not specific, and other recognized causes for it were identified in four cases. It is likely, however, that sarcoid tissue causes this pattern in some cases, and confirmation was obtained from cerebral biopsy in one. In six patients, the white matter changes were indistinguishable from those seen in multiple sclerosis. Contrast-enhanced CT in two patients showed diffuse meningeal involvement not seen with MRI. MRI is the investigation of choice in detecting parenchymal changes in the brain of patients with CNS sarcoidosis and may prove useful in monitoring treatment in such cases.

Prolonged neurogenic weakness in patients requiring mechanical ventilation for acute airflow limitation.

We describe three patients who required mechanical ventilation for severe acute exacerbations of obstructive airways disease. When treatment with sedatives and muscle relaxants was withdrawn, they exhibited profound generalized weakness and consequently required prolonged ventilation despite resolution of the airway obstruction. Clinical features were variable, but none of the patients developed failure of other organs and infection was confined to the lungs. All had electrophysiologic evidence of a predominantly motor axonal syndrome. One patient in whom sensory action potentials were abnormal may represent an unusually severe case of critical illness neuropathy occurring in the absence of systemic sepsis and multiple organ failure. In the other two cases, this diagnosis is made less likely by the complete absence of sensory involvement and in these patients the lesion appeared to be either in the most distal portion of the motor neuron or at the neuromuscular junction. In all three patients, resolution was slow but eventually complete. The etiology of the condition is not clear, but it seems to be distinct from the acute myopathy previously described in asthmatics who had received mechanical ventilation. It is important to recognize this phenomenon to avoid erroneous conclusions about the likelihood of the patient recovering from ventilator dependence. A prolonged weaning period is to be expected in such cases.

Strachan's syndrome: variation on a theme.

We report two patients of Afro-Caribbean origin with an ataxic neuropathy combined with visual loss and deafness. In previous reports of a similar syndrome most patients have been malnourished and have had mucocutaneous lesions, features which were absent in our patients.

Focal cranial nerve involvement in chronic inflammatory demyelinating polyneuropathy: clinical and MRI evidence of peripheral and central lesions.

Five cases of chronic inflammatory demyelinating polyneuropathy are described in which cranial nerve involvement accompanied a more generalized neuropathy. Clinical, electrophysiological, radiological and nerve biopsy findings are presented. Cranial nerve lesions in this form of polyneuropathy may be related to lesions of the peripheral nerves or of the central nervous system, when they may be accompanied by MRI evidence of more widespread CNS demyelinating lesions. In cases of early onset, the occurrence of focal cranial nerve lesions may serve to distinguish chronic inflammatory from inherited demyelinating polyneuropathies.

Accuracy and precision in the measurement of relaxation times from nuclear magnetic resonance images.

The accuracy (proximity to the true value) and precision (reproducibility) of relaxation times derived from nuclear magnetic resonance images were investigated. Two methods of deriving relaxation times were considered. A patient scanning protocol in which the minimum number of scans necessary for the calculation (three) were performed. Calculated T1 and T2 images were then formed. An animal (cat) protocol in which many more scans were performed. The data were read from the display and fitted by computer to the theoretical curves. The accuracy of the measurements was determined by an empirical method. A series of bottles with different concentrations of MnCl2 and CuSO4 in water were prepared and their relaxation times determined using the imager as a simple pulsed spectrometer. These values were compared with those derived from images. Over the normal range of tissue values (T1 less than 700 ms, T2 less than 200 ms) the animal protocol gave values of T1 up to 1% shorter than the true values. The T2 values were up to 5% shorter. Patient protocol values were up to 7% shorter for T1 and up to 20% shorter for T2. There was some difference between results for MnCl2 and for CuSO4 (particularly for patient T2s), suggesting that the results depend to a small extent on the T1/T2 ratio. The precision of the values was investigated by considering the standard deviations (SDs) of brain tissue measurements over populations of cats (animal protocols) and normal control subjects and multiple sclerosis patients (patient protocols). These were compared with the SDs of measurements of calibration bottles scanned with the patients. Standard deviations of 3% for T1 and 6% for T2 were found over 19 cats using the animal protocols; SDs of 7% for T1 and 14% for T2 were found over 15 normal control subjects using the patient protocols. Standard deviations of bottle measurements were similar to these figures. There are also variations between different subjects and different regions of the brain. There was no significant change between readings on the same patient in follow-up studies. Other sources of variation in the measurements made with the patient protocols were investigated by scanning phantoms. Noise in T1 and T2 images is about 2%. Spatial non-uniformity within slices is about 1% for T1 and 10% for T2. Non-uniformity between slices in multislice sets is 4% for T1 and 14% for T2. There is no long-term variation in measured values over 9 months; short-term variation is approximately 1%.

Multiple sclerosis presenting with progressive visual failure.

Progressive visual failure as the presenting feature of multiple sclerosis is described in five patients. The clinical features did not permit a distinction from visual loss due to compression. The finding of oligoclonal bands in the CSF at presentation is a useful pointer to the diagnosis, but is not specific and full investigation to exclude treatable causes of visual loss is essential.

Hereditary neuralgic amyotrophy associated with a relapsing multifocal sensory neuropathy.

A family with neuralgic amyotrophy (idiopathic brachial plexus neuropathy) associated with a multifocal sensory neuropathy is described. Four members over two generations were affected by neuralgic amyotrophy, inherited as an apparent autosomal dominant trait; two also had a multifocal relapsing sensory neuropathy with the clinical features of Wartenberg's migrant neuropathy.

Focal weakness following herpes zoster.

Three patients presented with focal weakness of an arm which followed segmental herpes zoster affecting the same limb. Neurophysiological investigations suggest that the site of the lesion lay at the root, plexus, or peripheral nerve level. This reflects the various ways in which the virus may affect the peripheral nervous system.

Guillain-Barré syndrome after herpes zoster infection: a report of 2 cases.

We report 2 patients with Guillain-Barré syndrome following infection with the varicella-zoster virus. Evidence from neurophysiological studies is provided and the literature is reviewed on the association between these conditions.

Hemiparetic multiple sclerosis.

Eight patients are described who presented with hemiparesis which involved the face in seven. Six of the eight subsequently developed clinically definite multiple sclerosis and in the remaining two patients multiple sclerosis was the likely diagnosis. Magnetic resonance imaging gave useful information about the site of the lesions responsible for the presenting syndrome and provided additional information in support of a diagnosis of multiple sclerosis.

T cell lymphocytosis associated with polymyositis, myasthenia gravis and thymoma.

Peripheral T cell lymphocytosis is a rare finding in association with malignant thymomas. In the majority of previous cases, the tumours have behaved aggressively with symptoms arising from local invasion. We describe a patient with ocular myasthenia gravis who presented with a rapidly progressive polymyositis and neuropathy and who was subsequently found to have a thymic mass and a mild T cell lymphocytosis. The thymoma did not give rise to local symptoms and showed no evidence of progression over a 14-month period of follow-up. The possibility of an underlying thymic tumour should be considered in any patient with chronic T cell lymphocytosis if the circulating cells show mature morphology and there is no molecular evidence of monoclonality.

Giant axonal neuropathy: observations on a further patient.

A further child with giant axonal neuropathy (GAN), abnormally curly hair and consanguineous parents is described. Of the 19 patients with GAN so far reported in the literature, six, including the present patient, have resulted from consanguineous marriages. This makes autosomal recessive inheritance of GAN highly probable. Our patient also exhibited cerebellar ataxia and signs of pyramidal tract damage; magnetic resonance brain imaging demonstrated abnormalities within the cerebellar and cerebral white matter. Myelinated nerve fibre density in the sural nerve was reduced to 6790/mm2 at age 8 years and had fallen to 3812/mm2 16 months later, indicating that progressive axonal loss occurs in GAN.

Relaxation times of apparently normal cerebral white matter in multiple sclerosis.

The magnetic resonance imaging (MRI) characteristics of the apparently normal cerebral white matter were studied in a group of 35 patients with clinically definite multiple sclerosis (MS). The proton relaxation times were compared with those in normal control subjects and patients with clinically isolated neurologic lesions of a type common in MS. Significant differences were found between all the patient groups and the control subjects. Changes in the cerebral white matter may be an early feature of MS.

Measurement of NMR relaxation times using the minimum number of scans.

NMR relaxation time measurements derived from a set of three multi-slice sequences (which can examine the whole brain in 30 min) have been investigated. T1 and T2 values are 5% and 20% too short, respectively. Noise in the measurements was less than 2%. Temporal instability was negligible. Spatial non-uniformity was 1% (T1) and 3% (T2) within a single slice but 4% (T1) and 14% (T2) from slice to slice. Variations in cerebral tissue measurements have also been investigated: T1 varies by 6% and T2 by 12% over a population of normal controls. There can be significant patient-patient and topographical variations.

Nuclear magnetic resonance. Its implications for the anaesthetist.

The theory and practice of clinical nuclear magnetic resonance (NMR) imaging is reviewed. Problems which the anaesthetist will encounter are considered, and recommendations are proposed. Possible uses of NMR in anaesthesia are discussed.

Involvement of the central nervous system in chronic inflammatory demyelinating polyneuropathy: a clinical, electrophysiological and magnetic resonance imaging study.

In a consecutive series of 30 patients with chronic inflammatory demyelinating polyneuropathy (CIDP) minor clinical evidence of CNS involvement was found in five. Cranial magnetic resonance imaging (MRI) was performed in 28 and revealed abnormalities consistent with demyelination in nine patients aged less than 50 years and abnormalities in five aged 50 years or over. Measurements of central motor conduction time (CMCT) were obtained in 18 and showed unilateral or bilateral abnormalities in six. It is concluded that subclinical evidence of central nervous system (CNS) involvement is common, at least in patients with CIDP in the United Kingdom, but that clinically evident signs of CNS disease are infrequent. The association of a multiple sclerosis-like syndrome with CIDP is rare.

MR brain scanning in patients with vasculitis: differentiation from multiple sclerosis.

We performed MR (magnetic resonance) brain imaging on 24 patients with a systemic vasculitis. MRI proved to be a sensitive method for detecting brain lesions (clinically silent or manifest) in these patients. The most frequent abnormalities were periventricular lesions seen in 12 cases. Such changes are not specific for vascular disease, and are often seen in multiple sclerosis. However, additional changes were commonly seen which suggested the correct diagnosis.

The early risk of multiple sclerosis following isolated acute syndromes of the brainstem and spinal cord.

A combined clinical and magnetic resonance imaging follow-up study was undertaken to determine the risk of early progression to multiple sclerosis in patients who present with clinically isolated lesions of the brainstem or spinal cord. Progression to multiple sclerosis was seen in 13 patients (57%) who had a brainstem syndrome and in 14 patients (42%) who had a spinal cord syndrome after mean intervals of 15 and 16 months, respectively. The risk of progression was increased by the presence of oligoclonal bands in the cerebrospinal fluid of patients with either syndrome and by the presence of disseminated brain lesions, as detected by magnetic resonance imaging, in those with a spinal cord syndrome. Follow-up revealed evidence of multiphasic disease in 24 (69%) of 35 patients who had disseminated lesions on magnetic resonance imaging scans at presentation, suggesting that multiple sclerosis is the usual cause of such lesions.