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BACKGROUND AND PURPOSE: Pilomyxoid astrocytoma (PMA) is a recently described variant of pilocytic astrocytoma (PA) with unique clinical and histopathologic characteristics. Because the histopathology of PMA is distinct from that of PA, we hypothesized that PMAs would display distinctive imaging characteristics. We retrospectively reviewed the imaging findings in a large number of patients with PMA to identify these characteristics. MATERIALS AND METHODS: CT and MR images, pathology reports, and clinical information from 21 patients with pathology-confirmed PMA from 7 institutions were retrospectively reviewed. CT and MR imaging findings, including location, size, signal intensity, hemorrhage, and enhancement pattern, were tabulated. RESULTS: Patients ranged in age from 9 months to 46 years at initial diagnosis. Sex ratio was 12:9 (M/F). Twelve of 21 (57%) tumors were located in the hypothalamic/chiasmatic/third ventricular region. Nine (43%) occurred in other locations, including the parietal lobe (2/21), temporal lobe (2/21), cerebellum (2/21), basal ganglia (2/21), and fourth ventricle (1/21). Ten (48%) tumors showed heterogeneous rim enhancement, 9 (43%) showed uniform enhancement, and 2 (9%) showed no enhancement. Five (24%) masses demonstrated intratumoral hemorrhage. CONCLUSION: This series expands the clinical and imaging spectrum of PMA and identifies characteristics that should suggest consideration of this uncommon diagnosis. One third of patients were older children and adults. Almost half of all tumors were located outside the typical hypothalamic/chiasmatic region. Intratumoral hemorrhage occurred in one quarter of patients. PMA remains a histologic diagnosis without definitive imaging findings that distinguish it from PA.

Several forms of motor neuron disease occurring in association with HIV infection have been described. Segmental proximal spinal muscular atrophy or brachial amyotrophic diplegia, a rare segmental variant of motor neuron disease with isolated bilateral upper extremity weakness, has previously been described in a single case report. We describe a patient who is HIV-seropositive presenting with this phenotype and illustrate novel findings on MRI of the cervical cord, consisting of focal atrophy and T2 hyperintense signal change involving the anterior grey matter. Additionally, a number of differences compared with patients without HIV presenting with this motor neuron disease variant are highlighted.

During recent historical times many Africans changed their diet to one based on maize. The grain is regularly contaminated by fungi which are toxigenic to domestic animals and birds. After one of the fungi, Diplodia maydis, in pure culture on maize, was added to the food of omnivorous primates there was demyelination of nerves, atrophy, degeneration and necrosis of muscle, and hepatitis. These preliminary results are applicable to veterinary and laboratory animal sciences. They may also be medically significant since neuromuscular syndromes of unknown cause are prevalent among Africans. Nerve conduction velocities and organ weights are defined for vervet monkeys.

A 21-month-old infant presented with acute obstructive hydrocephalus due to a large tuberculous abscess in the posterior fossa 3 months after starting treatment for miliary tuberculosis. Insertion of a ventriculo-peritoneal shunt resulted in some clinical improvement but subsequent neurological deterioration occurred due to massive enlargement of the tuberculous abscess despite apparently adequate antituberculosis therapy. Repeated drainage procedures of the abscess eventually resulted in resolution and clinical improvement. As part of the workup for poor weight gain and the unusual clinical course, the patient's acetylation status for isoniazid was determined and found to be very rapid. Doubling the daily dose of isoniazid was followed by a dramatic weight increase and further clinical improvement. Decreasing the load of tuberculous antigen by draining the abscesses and increasing the pulse exposure of isoniazid is the best possible explanation for the clinical improvement finally seen in this patient.

Neurological symptoms in childhood miliary tuberculosis are generally caused by underlying tuberculous meningitis (TBM), since the 2 conditions commonly occur concurrently. Cerebral infarction, a well-recognized complication of TBM, usually results from tuberculous periarteritis and secondary thrombosis. Neuropathological studies have demonstrated that the anterior cerebral circulation is more commonly affected than the arteries of the vertebro-basilar system, and basilar artery occlusion as a presenting manifestation of childhood miliary tuberculosis or TBM has not been described before. We report a 13-month-old infant who presented with fever and convulsions, terminating in acute decerebration after a second prolonged seizure 1 week after the onset of symptoms. Magnetic resonance (MR) imaging demonstrated density changes compatible with acute vertebro-basilar ischemia as well as multiple cerebral granulomas. A chest radiograph showed diffuse miliary tuberculosis. Postmortem examination confirmed this diagnosis and revealed acute occlusion of the basilar artery by an infected (septic) thromboembolus showing granulomatous inflammation, which most likely arose from an endocardial vegetation with identical histology.

Standardized postembedding immunoelectron microscopy was performed to demonstrate glial fibrillary acidic protein (GFAP) and vimentin in individual intermediate filaments to determine the diagnostic value of demonstrating ultrastructural and immunophenotypic characteristics of intermediate filaments in routine brain biopsy specimens. Dual expression of GFAP and vimentin was observed in the astroblastoma and astrocytes of Alexander's disease. The antigen availability for vimentin, however, was too low to allow reliable assessment of the GFAP:vimentin ratio in individual intermediate filaments and/or filament bundles. In meningioma, only vimentin positive intermediate filaments were found. GFAP positive intermediate filaments were present in all other specimens except the oligodendroglial components of the mixed glioma, which were devoid of intermediate filaments. GFAP positivity in the filamentous periphery and electron-dense core of Rosenthal fibers was demonstrated. Technical and tissue processing factors had a significant effect on particle density values obtained for individual specimens. Although the number, distribution, and density of glial intermediate filaments varies in different astroglial entities, correlation of particle density values determined by immunoelectron microscopy with relative GFAP concentrations in different lesions requires utmost caution. Nevertheless, application of the postembedding approach to routinely fixed biopsy specimens indicated an association of different entities with the exclusive presence of GFAP and/or vimentin in individual intermediate filaments, thus emphasizing the diagnostic value of intermediate filament typing for pathological characterization.

Besides the crucial information of topography, imaging provides a dynamic view of haematoma morphology whose microscopic correlates are increasingly expected of the neuropathologist. The CT scanner has a particular and enduring use in the demonstration of clotted or sedimented blood (provided mineralization is not a consideration), but is being overtaken by MR, together with the extraordinary complexities which that modality has brought to the subject of intracranial haemorrhage.

The suprasellar cistern is limited below by the hypophysis, dorsum sellae and cavernous sinus, and above by the floor of the third ventricle. It is bounded anteriorly by the sphenoid jugum and clinoids, on each side by the medial temporal lobes, and posteriorly by the cerebral peduncles, at which point the suprasellar, ambient and prepontine cisterns are continuous. Its principal contents include the infundibulum, optic nerves and chiasm, the internal carotid-circle vessels, and arachnoid tissue. Usually, the space is referred to as suprasellar by neurosurgeons, and para-or juxtasellar by radiologists. Most texts give a list of lesions which can occur in this region1,2, but for practical purposes the large majority of masses originate from the floor, mainly pituitary adenoma or craniopharyngioma, or a related cyst. Lesions from other structures, such as optic nerve and hypothalamic glioma, infundibular and vascular masses, are rare, and although granulomatous inflammation regularly affects the leptomeninges at this site, isolated inflammatory and parasitic masses are also very uncommon.

It appears from the literature on this subject1–4, most of which is in neurosurgical journals, that the difficulties in classifying developmental intracranial cysts, particularly those having a simple epithelial lining, are mainly the result of investigative inconsistencies, such as the application of a particular antibody, the use or lack of electron microscopy, and so on. It is clear, however, that whilst a correlative approach is essential, no combination of topography, imaging features and morphology is specific for any particular cyst, even with a distinctive lesion such as colloid cyst of the third ventricle.

The concentrated attention of a number of specialities, otorhinolaryngology in particular, has greatly enhanced the detail of clinical investigation in cranial lesions, but inevitably has had the effect of pathological compartmentalization, and access of the neuropathologist to many of these conditions tends to be restricted to cases involving the neurosurgeon. As is to be expected with epithelial and mesenchymal-proliferative lesions, signal characteristics are non-specific, approximating the common denomination of soft tissue in general, often with loss of differential contrast enhancement: thus meningioma invading muscle, for example, enhances less distinctively than usual (Figures 2.17 and 2.18).

In the following sections, the material presented has been restricted to the sort commonly encountered in purely neurosurgical practice. The effect of such arbitrary selection is immediately apparent with regard to vertebral lesions, where primary neoplasms are omitted; apart from discogenic disease the neuropathologist will only receive extradural tissues when parenchymal or radicular impingement occurs and, even then, primary osseous conditions are excluded, being normally handled by the orthopaedic surgeons. Conversely, the routine management of discogenic and other mechanical disturbances of root and cord function in most neurosurgical units, constitutes a unique area of extrameningeal pathology, which MR has made very much more relevant than formerly.

The characterization of primary or developmental cysts is discussed in section 3.1. All the main varieties with the exception of colloid cyst have been described in the posterior fossa, and it is worth recalling the histological and immunocytochemical similarities between that entity and the neurenteric cyst. Within the posterior fossa, arachnoid and neurenteric cysts are usually restricted to the subarachnoid space, the former most often within the dorsal cerebellomedullary and quadrigeminal plate cisterns (Figure 6.1), whilst the latter extends with multiple loculations, through the prepontine and cervical subarachnoid space. Intra-extraparenchymal and intraventricular locations are more in favour of neuroepithelial cyst (Figure 6.2). Epidermoidoma (see below), which is also the commonest of the congenital cysts, favours the prepontine-cerebellopontine cistern. Fluid which is Ti hyperintensive relative to CSF suggests protein secretion or keratin. In all these examples, spurious enhancement may be caused by compressed choroid and meninges, and all may be mimicked by cysticercus (Figure 6.8).

The advent of magnetic resonance imaging (MRI) has had the same profound effect on medical and surgical neurology that computerized tomography (CT) had, when that modality first appeared. Compared with CT, however, MR images are both more detailed and more specific, whilst views in any axis are possible, the so-called multiplanar facility. That MRI has superseded CT in aspects of neurology is beyond doubt: yet CT continues to be a cost-effective investigation in many circumstances, and in most institutions the two modalities thrive side by side. Many patients, therefore, have undergone both types of imaging, and the diagnostic process oscillates between the terminologies of each. This assumption of parallel interpretation is made throughout the text.

To date, little has been published on the MR imaging of inflammatory disorders of the CNS, and our own experience in this area is still very limited. To assist the reader to understand the mechanisms involved in producing an MR signal, it will be helpful to present a general discussion of the inflammatory process, paying particular attention to associated pathologic changes that can influence the signal characteristics on MR images. Experience with CT is included.

Skeletal muscle morphology and mitochondrial oxidative phosphorylation capacity were examined in a family whose members showed very combinations of mental subnormality, cardiomyopathy and muscle weakness. Light and electron microscopic findings suggested a neuropathic process, while tests of mitochondrial function indicated a state of tight coupling of oxidative phosphorylation, a feature in marked contrast to those in biochemical studies so far reported.

Changes in the brain in subacute sclerosing panencephalitis (SSPE) as detected on computed axial tomography (CT) have so far been insufficiently assessed. An attempt was therefore made to correlate the clinical, neuroradiological and pathological findings in 5 consecutive, unselected cases, 4 of which were somewhat atypical. It is concluded that within the context of a degenerative neurological disorder of childhood, the CT findings in SSPE correlate well with clinical staging, and also illuminate certain aspects of the pathogenesis and dynamics of the disease process.

In spite of the fact that peripheral neuropathy is very common in alcoholics, the chronic proximal muscular weakness and wasting found in alcoholics have been ascribed to myopathy. A clinical, biochemical, and histological study of 13 patients provided evidence for neuropathy. Enzymic histochemistry of muscle demonstrated selective type 2 neurogenic atrophy with evidence of reinnervation.

In three cases of generalized muscle weakness, muscle biopsy revealed well-defined, non-caseating epithelioid granulomata with giant cells. In one of these patients there was, in addition, a high serum CPK and histological evidence of widespread muscle cell degeneration and regeneration, apparently unrelated to the granulomatous process. In a re-examination of the histopathology of these cases, using biopsy material from a fourth case of proven sarcoidosis as a standard, it was concluded that there are no special features of the granulomatous/giant cell process which permit the separation of the case of presumed polymyositis. However, it appeared that granulomata per se do not exert a significant ill effect on surrounding muscle cells, and that evidence of widespread degeneration of muscle cells is the important point of distinction.

Three patients who presented with weakness and wasting of the quadriceps muscles ('quadriceps myopathy'), are reported. In each, electrophysiological and biopsy studies revealed completely different pathological processes, including motor unit disease, polymyositis and muscular dystrophy. Double biopsies performed in 2 of the patients showed the disease process to involve upper as well as lower limbs. The diffuse and heterogeneous nature of this form of neuromuscular disease is confirmed.

Three cases are presented in which occult lymphoreticular malignant tumour spread to the spinal and cranial subarachnoid spaces inducing a problematic neurological illness characterised by poorly localised neuralgic pain, slowly progressive paresis and, in 2 patients, papilloedema with computed tomographic evidence of ventricular dilatation. Despite intensive investigations, diagnosis was only achieved at autopsy. A progressive disturbance of spinal and cranial nerve function should direct the attention of the clinician to the possibility of diffuse meningeal involvement by a malignant or inflammatory process.

Laminectomy, performed on a 46-year-old woman because of weakness and paresthesias of the lower limbs, showed multiple discrete yellow nodules on the nerve roots of the cauda equina. One of these lesions was excised and proved to be a granuloma consistent with the diagnosis of histiocytosis X.

A patient with McArdle's disease is reported in whome proximal muscle weakness began in the 7th decade. Other unusual features included the absence of muscle cramps at any stage, asymmetrical wasting of the shoulder girdle muscles and calf hypertrophy. Muscle biopsy revealed a vacuolar myopathy, absent phosphorylase staining and qualitatively low glycogen content.