Meninges: benign postoperative enhancement on MR images

In a group of 20 postcraniotomy patients who underwent magnetic resonance imaging performed with gadopentetate dimeglumine, 16 (80%) had nonneoplastic meningeal enhancement. This was seen as either enhancement of a local dural membrane or generalized meningeal enhancement. In a control group of 23 patients, only three (13%) had similar findings. The authors believe that postcraniotomy meningeal enhancement is most likely the result of a local inflammatory process or a diffuse chemical arachnoiditis caused by bleeding into the subarachnoid space at the time of surgery. The finding does not necessarily indicate leptomeningeal tumor spread or infection.

Ferromagnetism and MR imaging: safety of carotid vascular clamps

Metallic extracranial carotid vascular clamps of the Selverstone, Crutchfield, Poppen-Blaylock, Salibi, Kindt, and tantalum varieties have been placed for treatment of large, giant, or inoperable intracranial aneurysms. To ascertain what adverse effect, if any, MR imaging would have on these clamps, magnetic deflection at 1.5 T was measured for various carotid clamps. Marked magnetic deflection (and torque) was displayed by stainless steel Poppen-Blaylock clamps. Relatively mild magnetic deflection was displayed by the stainless steel Selverstone, Salibi, Crutchfield, and Kindt clamps. Three patients with previously placed carotid clamps (two Selverstone, one Salibi) and one patient with a nonferromagnetic tantalum carotid clip had cranial or cervical MR studies at field strengths ranging from 0.35 to 0.60 T. No patient experienced any discomfort or neurologic sequelae as a result of MR imaging. Although the ferromagnetic clamps created severe "black-hole" artifacts and image distortion within the cervical and facial regions, no significant image degradation was apparent during spin-echo imaging of the brain. The tantalum clip created a far smaller MR artifact than did ferromagnetic clamps and allowed effective spin-echo and gradient-echo imaging in the cervical region. Our findings indicate that most patients with carotid vascular clamps (and nonferromagnetic clips) can probably be imaged safely with MR.

Alzheimer's disease: theories of causation

There are many theories to explain the cause of Alzheimer's disease. None is mutually exclusive of the others, and it may be that all are correct. The only problem may be that we do not understand which is the primary cause and which are the secondary effects of the primary abnormality in the disease. It is almost certain that Alzheimer's disease, as we recognize it today, is heterogeneous. One has only to think of the early-onset and late-onset familial cases to realize that this is so. All of the theories have experimental evidence to support them, and all have generated experiments to substantiate them. Some of them have generated potential concepts for treatment, none of which at present have proved to be successful. When in the end the underlying etiology of the condition is discovered, it will be possible to fit all of the experimental observations into place. It appears at present that the most likely breakthroughs in our understanding will come from detailed sequencing of the paired helical filaments and from breakthroughs in the field of molecular genetics studying the gene for familial Alzheimer's disease.

MR imaging of neurocysticercosis

Twenty-six patients with neurocysticercosis were studied with MR imaging to correlate their clinical presentation with the location and appearance of their neurocysticercosis lesions. Intraventricular cysts were present in 14 patients (54%), parenchymal cysts were present in 18 (69%), and intraventricular together with parenchymal cysts were present in six (23%). Intraventricular cysts were detected by mass effect, ventricular obstruction, detection of a cyst rim, and/or CSF flow void adjacent to the cyst. The intensity of most intraventricular and parenchymal cysts presumed to be viable was similar to that of CSF on both T1- and T2-weighted sequences. Cysts presumed to be degenerated had increased signal intensity on T1-weighted images, probably resulting from increased protein content. Pericystic high signal intensity surrounding lesions of various ages was seen on both proton-density- and T2-weighted images and represents gliosis, edema, and inflammation. Patients with parenchymal cysts had symptoms of seizures, while those with intraventricular cysts generally had symptoms related to obstructive hydrocephalus. Aqueductal stenosis, seen in 10 patients (38%), was possibly due to ependymal inflammation or adhesions caused by prior ventricular infection by neurocysticercosis. One patient with the racemose form of neurocysticercosis demonstrated abundant cyst wall proliferation resulting in obstructive hydrocephalus. In six patients scanned 1-6 months after oral praziquantel therapy, there was no change in the MR appearance of intraventricular cysts, while some parenchymal cysts showed evidence of degeneration. We found MR to be useful in detecting the cysts of neurocysticercosis and the accompanying signs of cyst degeneration and pericystic inflammation. MR was inferior to CT in the detection of parenchymal calcifications.

Quantitative measures of neurological function in chronic neuromuscular diseases and ataxia

Interexaminer and intraexaminer reliability were determined for 30 quantitative measures of neurological function, including sensory threshold, tendon reflexes, maximum isometric strength, and timed tests and coded ratings of functional ability, in patients with Charcot-Marie-Tooth disease (n = 30), idiopathic polyneuropathy (n = 16) and spinocerebellar degeneration (n = 30). Five of 6 sensory and reflex measures had interexaminer reliability greater than 0.80 when the neurologists' examinations were 1 h apart; 2 of 7 achieved this level when the examinations were separated by 1 month. Interexaminer reliability between physical therapists was greater than 0.80 for 19 of 20 measures of strength and functional ability. Intraexaminer reliability coefficients greater than 0.80 were found for 13 of 24 sensory and reflex measures, 28 of 30 isometric strength measures, 24 of 30 timed tests and 5 of 6 coded ratings of functional ability. Electro-oculography, oral diadochokinetic syllable rates, hand and foot accelerometry, and tracings of sine and square waves were examined as quantitative indices of ataxia for patients with spinocerebellar degeneration. Of 11 measures of ataxia, only the oral diadochokinetic syllable rate test had acceptable reliability.

Decreased DNA repair in familial Alzheimer's disease

Alterations in the capacity of a cell to repair DNA lesions play an important role in a number of human diseases. We and others have demonstrated defective DNA repair of alkylation damage in cells from patients with Alzheimer's disease. It has been hypothesized that this defect is related to the cause of Alzheimer's disease and results in the accumulation of lesions in the central nervous system neurons. One prediction of this hypothesis is that in dominantly inherited Alzheimer's disease, the repair defect will be present in half of the offspring of affected patients long before they develop symptoms of the disease. In order to test the hypothesis that decreased DNA repair is responsible for familial Alzheimer's disease and their at-risk offspring we have studied DNA repair in these individuals after exposure of lymphoblasts to alkylating agents. Our results indicate that cell lines from affected patients repair significantly less damage in 3 h than cell lines from healthy controls. A small number of at-risk individuals were also studied and some of these had lower levels of repair, although more cell lines from individuals in this group must be studied. These findings provide further support for defective DNA repair playing a role in the pathogenesis of Alzheimer's disease.

Common pitfalls in magnetic resonance imaging of the knee

Magnetic resonance examinations of 200 knees were studied retrospectively to determine the frequency with which normal ligamentous and tendinous structures mimicked pathological changes in the meniscus or elsewhere in the knee. Although the course of the transverse geniculate ligament simulated a tear of the anterior horn of the lateral meniscus on forty-four (22 per cent) of the sagittal magnetic-resonance scans, no tear of the lateral meniscus was found in the nine patients in this group who had an arthroscopic examination. The normal anatomy of the meniscofemoral ligament varies greatly. The ligament of Humphry, the anterior branch of the meniscofemoral ligament, was visualized on sixty-six (33 per cent) of the magnetic resonance scans. The ligament of Wrisberg, the posterior branch of the meniscofemoral ligament, was identified on sixty-five (32.5 per cent) of the scans. On sagittal images, these ligamentous branches can be mistaken for osteochondral or meniscal fragments. However, a loose body was found in only one of the thirty-two patients who had an arthroscopic examination after the ligament of Humphry or of Wrisberg was seen on the magnetic resonance image. The bursa of the popliteus tendon simulated a tear of the posterior horn of the lateral meniscus in fifty-five (27.5 per cent) of the studies, although an actual tear of the posterior horn was found in only two of the eleven patients who had an arthroscopic examination.(ABSTRACT TRUNCATED AT 250 WORDS)

The anatomic basis of vertebrogenic pain and the autonomic syndrome associated with lumbar disk extrusion

Extruded lumbar intervertebral disks traditionally have been classified as posterior or central in location. A retrospective review of 250 MR imaging examinations of the lumbar spine that used mid- and high-field imagers revealed 145 positive studies, which included a significant number of extrusions extending anteriorly. With the lateral margin of the neural foramen/pedicle as the boundary, 29.2% of peripheral disk extrusions were anterior and 56.4% were posterior. In addition, a prevalence of 14.4% was found for central disk extrusions, in which there was a rupture of disk material into or through the vertebral body itself. The clinical state of neurogenic spinal radiculopathy accompanying posterior disk extrusion has been well defined; however, uncomplicated anterior and central disk extrusions also may be associated with a definite clinical syndrome. The vertebrogenic symptom complex includes (1) local and referred pain and (2) autonomic reflex dysfunction within the lumbosacral zones of Head. Generalized alterations in viscerosomatic tone potentially may also be observed. The anatomic basis for the mediation of clinical signs and symptoms generated within the disk and paradiskal structures rests with afferent sensory fibers from two primary sources: (1) posterolateral neural branches emanating from the ventral ramus of the somatic spinal root and (2) neural rami projecting directly to the paravertebral autonomic neural plexus. Thus, conscious perception and unconscious effects originating in the vertebral column, although complex, have definite pathways represented in this dual peripheral innervation associated with intimately related and/or parallel central ramifications. It is further proposed that the specific clinical manifestations of the autonomic syndrome are mediated predominantly, if not entirely, within the sympathetic nervous system. The directional differentiation of lumbar disk extrusions by MR, together with a clarification and appreciation of the accompanying clinical somatic and autonomic syndromes, should contribute both to understanding the specific causes as well as to establishing the appropriate treatment of acute and chronic signs and symptoms engendered by many nonspecific disease processes involving the spinal column.

Magnetic resonance imaging of cardiac sarcomas

Two patients with cardiac sarcomas were evaluated with magnetic resonance imaging (MRI). In both cases, MRI provided more information regarding the extent of the tumor than computed tomography, two-dimensional echocardiography, or angiography.

Comparison of cocurrent and countercurrent flow-related enhancement in MR imaging

Patterns of flow-related signal loss and enhancement have been observed in fluid moving perpendicular to the imaging plane on multi-section-acquisition magnetic resonance images. These patterns depend on whether the flow is in the same direction (cocurrent) or opposite (countercurrent) to the direction of sequential section excitation. For a given velocity, flow-related enhancement penetrates deeper into the imaging volume with countercurrent flow than with cocurrent flow. The signal intensity of inner sections is generally greater with countercurrent flow than with cocurrent flow and depends on the velocity. These effects were investigated quantitatively with phantom studies and correlated with theoretical predictions. It was found that the limited penetration of flow-related enhancement with cocurrent flow is a consequence of recently saturated upstream protons flowing into the section to be excited. The flow-related enhancement penetrates farther with countercurrent flow, because inflowing spins have had a greater period of time to recover from the saturating effect of the radio-frequency pulse. Because different laminae have different time intervals to recover magnetization, this also accounts for the observation of concentric rings representing laminar flow in the countercurrent direction.

MR imaging of callosal and corticocallosal dysgenesis

Callosal dysgenesis implies a malformation of the corpus callosum with origins in the embryogenesis of the telencephalon. A retrospective review of 15 cases of callosal dysgenesis revealed three distinct categories: agenesis (three subjects), hypogenesis (nine subjects), and hypoplasia (three subjects). The basis of this distinction rests upon considerations of neural tube closure, formation and maintenance of the inductive plate of the massa commissuralis, and migration of the neuronal elements of the cerebral cortex responsible for the projection of the commissural fibers of the corpus callosum. These processes are somewhat interdependent in their expression and consequence, resulting in a unique mosaic of callosal and cortical gray matter and hemispheric white matter configurations that have individually varying clinicoradiologic manifestations.

Double-blind controlled trials of Cronassial in chronic neuromuscular diseases and ataxia

We report three 12-month, double-blind, three-phase studies comparing the effect of placebo and 40 mg and 100 mg IM daily of purified bovine brain gangliosides (Cronassial) in chronic neuromuscular diseases. Thirty patients with Charcot-Marie-Tooth disease, 16 with idiopathic polyneuropathy, and 30 with spinocerebellar degeneration had neuromuscular function measured monthly by quantitative testing of motor and sensory function, coordination, and electrophysiologic factors. Analysis of these studies, and of longer term (up to 2 years) open studies of 100 mg daily of Cronassial in 67 patients failed to show therapeutic efficacy of Cronassial. Statistical power calculations indicated that five of the 37 measures had greater than a 70% chance of detecting a 20% difference in the rate of progression of the active-drug and placebo groups. A number of measures significantly improved during prolonged placebo treatment, suggesting that the placebo effect has a strong influence on "objective" measures of neuromuscular function.

MR imaging in patients with intracranial aneurysm clips

Four patients with intracranial aneurysm clips made from a variety of alloys were studied without incidence by MR imaging at field strengths ranging from 0.35 to 0.6 T. Knowledge of the type of alloy used in the manufacturing of an aneurysm clip is important in determining whether the clip will or will not deflect in a magnetic field. Ferromagnetic clips show deflection and torque in a magnetic field and have the potential to dislodge from the aneurysm. Nonferromagnetic or weakly ferromagnetic aneurysm clips such as the Sugita (Elgiloy), Yasargil (316 LVM stainless steel), Heifetz (Elgiloy), Yasargil (Phynox), and Vari-Angle McFadden (MP35N) do not deflect or deflect weakly in the magnetic field and therefore would not be expected to dislodge during MR. The option of imaging many patients with intracranial aneurysm clips with MR extends the usefulness of the technique to a previously excluded population.

Low-artifact intravascular devices: MR imaging evaluation

Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible.

Iron accumulation in the basal ganglia following severe ischemic-anoxic insults in children

Increased iron deposition is described in four children following severe ischemic-anoxic insult and subsequent resuscitation. All cases demonstrated on T2-weighted magnetic resonance images areas of hypointensity in the basal ganglia, thalami, and white matter that were attributed to iron deposition. Associated areas of hyperintensity were also seen in the periventricular and subcortical white matter, and these were attributed to gliosis. In one case calcium deposition was also present within the areas of hypointensity. These findings suggest that after anoxic-ischemic damage, normal axonal transportation of brain iron can no longer occur. This may lead to increased accumulation of iron centrally at the sites of iron uptake in the basal ganglia and in the white matter. Additional iron deposition may occur more rapidly due to direct injury by lipid peroxidation degradation products catalyzed by iron.

Normal and abnormal white matter maturation

The unique ability of MR to demonstrate both normal and abnormal white matter maturation with a high degree of sensitivity makes it an indispensable tool with which to evaluate children with clinical developmental delay or suspected dysmyelinating processes. Because the noninvasive nature of MRI allows sequential studies to be performed without additional risk to the patient, it offers an unprecedented opportunity to study the process of myelination in normal infants, developmentally delayed infants and to better understand the dysmyelinating disorders, a relatively rare, poorly understood group of diseases.

Deep white matter infarction: correlation of MR imaging and histopathologic findings

Focal and confluent areas of periventricular hyperintensity have been reported on magnetic resonance (MR) images in 30% of patients over 60 years of age. In order to better understand the pathologic basis of these lesions, the authors studied 14 formalin-fixed brains with MR imaging. Multiple focal areas of hyperintensity were identified in the periventricular white matter in three of the 14 brains studied (21%). Subsequent gross and microscopic pathologic examination of both hyperintense and normal-intensity areas was performed on 87 tissue sections. The larger lesions were characterized centrally by necrosis, axonal loss, and demyelination and therefore represent true infarcts. Reactive astrocytes oriented along the degenerated axons were identified at distances of up to several centimeters from the central infarct. This is called isomorphic gliosis and is associated with increased intensity on T2-weighted images that increases the apparent size of the central lesion.

MR evaluation of early myelination patterns in normal and developmentally delayed infants

This study demonstrates the ability of MR imaging to show progression of myelination in 64 infants and young children (ages 4 days to 36 months). T2-weighted spin-echo pulse sequences, frequently used for routine screening of intracranial disease, were used. Gray-white matter differentiation was seen in all patients, and changes occurring with age were documented. Three distinct patterns were seen, and age ranges were established for each pattern in developmentally normal children: (1) infantile (birth-6 months); (2) isointense (8-12 months); and (3) early adult (10 months onward). There was a statistically significant difference between the age ranges of the normal and developmentally delayed children showing all three patterns. These data should be helpful for identifying and following sequentially both infants with clinically suspected developmental delay and those with dysmyelinating or demyelinating disease.

Proximal chronic inflammatory polyneuropathy with multifocal conduction block

The pathological findings in proximal and distal nerve biopsy specimens are described in a patient with the clinical and electrophysiological features of chronic inflammatory polyneuropathy with multifocal conduction block. Proximal onion bulb hypertrophic changes in the brachial plexus were associated with inflammatory cell infiltrates. In contrast, the sural nerve biopsy specimen showed a mild picture of mixed axonal degeneration and demyelination-remyelination without inflammatory infiltration.

Early-onset benign autosomal dominant limb-girdle myopathy with contractures (Bethlem myopathy)

We report a large French-Canadian kindred with 33 affected members in six generations showing early-onset autosomal dominant limb-girdle myopathy and contractures. This myopathy is unique because of its benign course, with many members only minimally impaired even in old age. Examination of affected members revealed mild to moderate proximal weakness and wasting. Contractures were observed at the elbows and ankles in all, while in some they were more widespread. Serum CK was either normal or slightly raised, and electrodiagnostic studies suggested a primary myopathy. Muscle biopsy revealed nonspecific features of a myopathy without fiber necrosis or regeneration. Cardiac involvement was absent clinically in all patients and at autopsy in two affected individuals. The similarities between four previously reported families and our own establishes this myopathy as a distinct clinicogenetic entity, for which we propose the name "Bethlem myopathy."