Supratentorial and pontine MRI abnormalities characterize recessive spastic ataxia of Charlevoix-Saguenay. A comprehensive study of an Italian series

BACKGROUND AND PURPOSE

The autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset neurodegenerative disorder caused by mutations in the SACS gene. The disease, first described in Canadian families from Québec, is characterized by cerebellar ataxia, pyramidal tract involvement and peripheral neuropathy.

METHODS

Analysis of SACS gene allowed the identification of 14 patients with ARSACS from 13 unrelated Italian families. Clinical phenotype, gene mutations and magnetic resonance imaging (MRI) findings were analysed.

RESULTS

We found 16 novel SACS gene mutations, including a large in-frame deletion. The age at onset was in infancy, but one patient presented the first symptoms at age 32. Progression of the disease was variable, and increased muscle tone was mostly recognized in later stages. Structural MRI showed atrophy of the superior cerebellar vermis, a bulky pons exhibiting T2-hypointense stripes, identified as the corticospinal tract (CST), thinning of the corpus callosum and a rim of T2-hyperintensity around the thalami in 100% of cases. The presence of iron or other paramagnetic substances was excluded. Diffusion tensor imaging (DTI) revealed grossly over-represented transverse pontine fibres (TPF), which prevented reconstruction of the CST at this level (100% of cases). In all patients, significant microstructural alterations were found in the supratentorial white matter of forceps, cingulum and superior longitudinal fasciculus.

CONCLUSIONS

Our findings further enlarge the genetic spectrum of SACS mutations and widen the study of clinical phenotype. MRI characteristics indicate that pontine changes and supratentorial abnormalities are diagnostic. The over-representation of TPF on DTI suggests a developmental component in the pathogenesis of the disease.

Decreased diffusivity in the caudate nucleus of presymptomatic huntington disease gene carriers: which explanation?

BACKGROUND AND PURPOSE

The neostriatum is known to be affected in HD. In this work, our aim was to determine whether microstructural and volumetric alterations occur in the neostriatum of presymptomatic HD gene carriers and in patients with early-stage HD.

MATERIALS AND METHODS

We studied a group of 15 presymptomatic gene carriers who were far from the estimated symptom onset (16% probability of developing the disease within 5 years), a group of 9 patients with early symptomatic HD, and 2 groups of age-matched controls. Volumetric MR imaging and DWIs were acquired, and statistical analyses were performed on the volumes of the caudate nucleus and putamen and on the corresponding MD measurements.

RESULTS

Neostriatal volumes were significantly smaller in both presymptomatic HD gene carriers and symptomatic patients with respect to controls. However, whereas the diffusivity in the caudate nucleus was increased in the symptomatic patients, it was decreased in the presymptomatic gene carriers.

CONCLUSIONS

Altered diffusivity and reduced volume of the caudate nucleus in presymptomatic HD gene carriers indicate that the neostriatum is affected well before the onset of symptoms. The observed initial decrease and subsequent increase of MD might be related to the combined effect of increased oligodendroglial population, putatively a developmental abnormality, and incipient neurodegeneration.

Diffusion tensor imaging shows different topographic involvement of the thalamus in progressive supranuclear palsy and corticobasal degeneration

BACKGROUND AND PURPOSE

In progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), postmortem studies show different topographic involvement of the thalamus, basal ganglia, and their cortical connections. Diffusion tensor imaging (DTI) is an MR imaging technique sensitive to gray and white matter microstructure integrity. This study was performed to determine whether DTI may demonstrate microstructural differences between PSP and CBD, particularly within the thalamus and its cortical connections.

MATERIALS AND METHODS

Nine patients with probable PSP, 11 with probable CBD, and 7 controls formed the study group. Apparent diffusion coefficient average (ADC(ave)) and fractional anisotropy (FA) values were measured in regions of interest positioned in the ventrolateral (motor), medial, anterior, and posterior regions of the thalami, basal ganglia, fronto-orbital white matter, cingulum, supplementary motor area (SMA), and precentral and postcentral gyri in patients and controls.

RESULTS

In PSP, ADC(ave) values were increased in several areas: the thalamus, particularly in its anterior and medial nuclei; cingulum; motor area; and SMA. FA values were particularly decreased in the fronto-orbital white matter, anterior cingulum, and motor area. In CBD, ADC(ave) was increased in the motor thalamus, in the precentral and postcentral gyri, ipsilateral to the affected frontoparietal cortex, and in the bilateral SMA. FA was mainly decreased in the precentral gyrus and SMA, followed by the postcentral gyrus and cingulum.

CONCLUSIONS

In patients with PSP, thalamic involvement was diffuse and prevalent in its anterior part, whereas in CBD involvement was asymmetric and confined to the motor thalamus. DTI may be useful in the differential diagnosis of these 2 parkinsonian disorders.

White matter involvement in idiopathic Parkinson disease: a diffusion tensor imaging study

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) offers a unique window on the connectivity changes, extending beyond the basal ganglia, which accompany the cognitive symptoms of Parkinson disease (PD). The primary purpose of this study was to assess the microstructural damage to cerebral white matter occurring in idiopathic PD.

MATERIALS AND METHODS

Our sample included patients with PD without dementia (n = 10; Hoehn and Yahr stages I and II; Unified Parkinson Disease Rating Scale, 20.5 +/- 8.3; and Mini-Mental State Examination, 28.3 +/- 1.5) and age-matched healthy control subjects (n = 10). DTI was performed on a 1.5T scanner, and mean diffusivity (MD) and fractional anisotropy (FA) maps were obtained. Regions of interest (ROIs) were drawn on the major fiber bundles as well as on gray matter nuclei.

RESULTS

In patients, the MD was increased at borderline significance in the substantia nigra but was unaltered in the thalamus, globus pallidus, putamen, and in the head of the caudate nucleus. The FA and MD were unaltered in the corticospinal tract in the midbrain and at the level of the internal capsule, and in the splenium of the corpus callosum. By contrast, the MD was increased and the FA was decreased in the genu of the corpus callosum and in the superior longitudinal fasciculus; in the cingulum, only the MD was altered. The observed changes were not significantly lateralized.

CONCLUSIONS

Widespread microstructural damage to frontal and parietal white matter occurs already in the early stages of PD.

A novel phenotype of sporadic Creutzfeldt-Jakob disease

An atypical case of sporadic Creutzfeldt-Jakob disease (CJD) is described in a 78-year-old woman homozygous for methionine at codon 129 of the prion protein (PrP) gene. The neuropathological signature was the presence of PrP immunoreactive plaque-like deposits in the cerebral cortex, striatum and thalamus. Western blot analysis showed a profile of the pathological form of PrP (PrP(Sc)) previously unrecognised in sporadic CJD, marked by the absence of diglycosylated protease resistant species. These features define a novel neuropathological and molecular CJD phenotype.

Diffusion tensor imaging of spinocerebellar ataxias types 1 and 2

BACKGROUND AND PURPOSE

Structural MR imaging does not enable reliable differentiation of spinocerebellar ataxia (SCA) types 1 and 2 (SCA1 and SCA2), and imaging may be normal during the first years after the onset of symptoms. We aimed at determining whether measurements of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) may enable their differentiation.

MATERIALS AND METHODS

We enrolled 14 patients with SCA1, 11 with SCA2, and 9 age-matched controls. Diffusion tensor imaging (DTI) was performed on a 1.5T scanner, with b = 1000s/mm2 and 12 directions. ADC and FA were measured by means of regions of interest, positioned in the corticospinal tract at the level of the cerebral peduncle and at the level of the pons, in the transverse pontine fibers, in the superior and middle cerebellar peduncle, and in the hemispheric cerebellar white matter.

RESULTS

With respect to controls, the ADC was significantly elevated in the middle cerebellar peduncle and in hemispheric white matter in SCA1, and in all regions under consideration in SCA2. It was significantly higher in SCA2 than in SCA1 in all regions under consideration. With respect to controls, the FA was significantly reduced in all regions under consideration in SCA1 and in SCA2. It was significantly lower in SCA2 than in SCA1 in the transverse pontine fibers and in the corticospinal tract at the level of the cerebral peduncle. Correlations with clinical scores were found.

CONCLUSIONS

DTI did not enable differentiation between SCA1 and SCA2. However, strongly significant differences between the 2 subtypes and with respect to controls and correlations with clinical scores were found.

MR spectroscopy, functional MRI, and diffusion-tensor imaging in the aging brain: a conceptual review

In vivo magnetic resonance spectroscopy (MRS), functional magnetic resonance imaging (fMRI), and diffusion-tensor imaging (DTI) have recently opened new possibilities for noninvasively assessing the metabolic, functional, and connectivity correlates of aging in research and clinical settings. The purpose of this article is to provide a conceptual review intended for a multidisciplinary audience, covering physical principles and main findings related to normal aging and senile cognitive impairment. This article is divided into 3 sections, dedicated to MRS, to fMRI, and to DTI. The spectroscopy section surveys physiological function of the observable metabolites, concentration changes in normal aging and their interpretation, and correlation with cognitive performance. The functional MRI section surveys the hemispheric asymmetry reduction model from compensation and de-differentiation viewpoints, memory encoding, retrieval and consolidation, inhibitory control, perception and action, resting-state networks, and functional deactivations. The DTI section surveys age-related changes, correlation with behavioral scores, and transition to cognitive impairment.

Imaging degeneration of the substantia nigra in Parkinson disease with inversion-recovery MR imaging

BACKGROUND AND PURPOSE

Visualizing with MR imaging and obtaining quantitative indexes of degeneration of the substantia nigra in Parkinson disease have been long-sought goals. We investigated the potential role of area and T1 contrast measurements in differentiating patients from controls and their age-related changes.

METHODS

Eight patients with Parkinson disease, 8 age-matched controls, and 8 young controls were imaged. We obtained the pixel-wise difference between 2 sets of inversion-recovery images, acquired parallel to the bicommissural plane, with different inversion times. Pixel-intensity ratios between lateral and medial nigral regions, and nigral area and substantia-nigra/midbrain area ratios were computed.

RESULTS

Compared with that of controls, loss of substantia nigra was evident in patients, its borders taking a smoother and more irregular appearance. Patients were characterized by a lateral-to-medial gradient, due to reduced hypointensity of the lateral portion of the substantia nigra and relative sparing of its medial portion. The visible nigral area was significantly smaller in patients compared with matched controls (P = .04). The substantia nigra/midbrain area ratio enabled considerably better separation (P = .0001). The lateral/medial pixel-intensity ratio was significantly higher in patients compared with matched controls (P = .01) and in young controls compared with age-matched controls (P = .01).

CONCLUSION

Inversion-recovery sequences may provide a convenient way to visualize nigral degeneration. Relative area and pixel-intensity measurements may integrate other techniques (such as diffusion-tensor imaging on nigrostriatal pathways) in the neuroradiologic diagnosis and follow-up of Parkinson disease by quantitatively assessing the degeneration of the substantia nigra.

Dendritic cells pulsed with glioma lysates induce immunity against syngeneic intracranial gliomas and increase survival of tumor-bearing mice

In recent years, the use of dendritic cells (DC), the most powerful antigen presenting cells, has been proposed for the creation of vaccines against gliomas. This approach has been demonstrated to be safe and non-toxic in phase I or I-II trials (2, 3). Immunotherapy plays a central role in the search for new treatments for glioblastoma multiforme (GBM). In particular, several phase I studies have been performed using DC pulsed by GBM proteins as a vaccine for patients with relapsing GBM. The studies demonstrated that DC vaccination is safe and may produce a significant increase in overall survival. As the first step in the preparation of appropriate conditions for a clinical evaluation in Italy, we have performed pre-clinical experiments on immune-competent mice injected intra-cerebrally with syngeneic GL261GBM cells and treated subcutaneously and intra-tumorally with DC loaded with a GL261 homogenate. These results show that vaccination with DC pulsed with a tumor lysate increases considerably survival in mice bearing intracranial glioblastomas and supports the development of DC-based clinical trials for patients with glioblastomas that do not respond to standard therapies.

Iron chelation therapy in aceruloplasminaemia: study of a patient with a novel missense mutation

We describe a novel missense mutation of ceruloplasmin in a patient with aceruloplasminaemia causing the replacement of a neutral amino acid (phenylalanine) with a polar one (serine) at position 198, probably leading to abnormal folding and secretion of the protein. The patient showed mild microcytic anaemia, mild hepatic iron overload, and marked brain iron overload. Six months of therapy with deferiprone was ineffective in removing iron from the tissues. Deferoxamine was more efficient in removing excess iron from the liver but aggravated the disease related anaemia. After more than one year of chelation treatment, the brain magnetic resonance imaging signal did not change. Overall, these findings indicate that treatment of iron overload in aceruloplasminaemia is a difficult challenge and that new iron chelators, more efficient in crossing the blood-brain barrier, are needed.

Neuroradiological features of vertigo

The diagnostic pathway in a patient with vertigo starts with the accurate evaluation of medical history followed by a general physical and neurological examination. This step can often lead to the identification of the correct cause of the disease or, at least, to a distinction between peripheral and central vertigo. Neuroradiological investigations have to be considered as elective diagnostic procedures and include: computed tomography (CT), magnetic resonance (MR), MR angiography (MRA), angiography. For the diagnosis of peripheral vertigo, benign paroxysmal positional vertigo, labyrinthitis, Meniere disease, perilymphatic fistula, local trauma, toxic labyrinthitis, acute otitis media and chronic middle ear effusion,the role of imaging techniques is controversial. CT and MR are performed to rule out other pathologies and to confirm the diagnosis. Increased resolution and application of special MR sequences enhancing the intralabyrinthine fluids have enabled more detailed analysis of labyrinthine structures and pathology. Both T2 and T1 contrast sequences are necessary. A high resolution CT study is required when otitis media is suspected and in the follow-up of post-traumatic vertigo. The causes of central vertigo are numerous and include: vertebro-basilar circulation vascular events, multiple sclerosis (MS), migraine-associated vertigo, cerebellar and brainstem tumors, CNS infections. Among them cerebrovascular ischemia and multiple sclerosis are the most frequent. In these situations imaging studies become mandatory. CT can diagnose most cerebellar hemorrhages and some cerebellar and brainstem acute ischemia, enhanced MR has proved to be the most sensitive tool to detect posterior fossa lesion. Diffusion-weighted MR can reveal acute ischemic changes before routine MR. There has been evidence that MR angiography, providing angiogram-like images of the intracranial vessels may sometimes avoid invasive angiography. MRA resolution is not as good as traditional angiography and may also be compromised by movements and other artifacts. Selective angiography of the posterior circulation is often indicated for therapeutic decisions.

Pathogenic effect of an intermediate-size SCA-6 allele (CAG)(19) in a homozygous patient

SCA6 is caused by CAG expansion in the alpha 1A voltage-dependent calcium channel subunit gene. The authors studied an Italian family in which one patient carried a fully expanded SCA6 allele with 26-CAG repeats, whereas the other affected family member was homozygous for an intermediate-size allele of 19-CAG repeats. Three family members, heterozygous for the intermediate allele, were clinically unaffected. The findings demonstrate a dose-dependent pathogenic effect of an intermediate CAG expansion in the SCA6 gene.

Imaging dementias

Dementia is the progressive loss of intellectual functions due to involvement of cortical or subcortical areas. Specific involvement of certain brain areas in the different diseases leads to impairment of different functions, e. g., memory, language, visuospatial abilities, and behavior. Magnetic resonance imaging and other neuroradiological studies may indicate which structures are mainly or selectively involved in a demented patient, thus allowing clinical-radiological correlations. Clinical presentation and evolution of the disease, supported by imaging studies, may lead to a highly probable diagnosis. The most common disorders, or the most relevant from the neuroradiological point of view, such as Alzheimer's disease, frontotemporal dementia, vascular dementias, dementia associated with parkinsonism, Huntington's disease, Creutzfeldt-Jakob disease, and normal-pressure hydrocephalus, are briefly discussed.

Clinical and neuroradiological aspects of Sneddon's syndrome and primary antiphospholipid antibody syndrome. A follow-up study

We performed a study to investigate differences and similarities between patients with Sneddon's syndrome and those with primary antiphospholipid syndrome (PAS), by clinical follow-up, magnetic resonance imaging (MRI) and angiography. Nine patients with Sneddon's syndrome and 11 patients with PAS were assessed at diagnosis and followed for a mean of 6 years. The clinical and MRI findings indicated that Sneddon's syndrome and PAS are distinct entities. Patients with Sneddon's syndrome had a progressive clinical course with increasing disability and cognitive deterioration; patients with PAS had a more benign course. Infarcts in territories of the main cerebral arteries were frequent in PAS, while leukoaraiosis and small lacunar infarcts were more common in Sneddon's syndrome. In 3 of 7 women initially diagnosed with PAS, the diagnosis was changed to systemic lupus erythematosus during follow-up. Differential diagnosis of Sneddon's syndrome and PAS is important, as early therapy is effective for the latter, more benign, condition.

Clinical and magnetic resonance imaging findings in chronic sensory ganglionopathies

Twenty-two of 29 patients with chronic sensory ataxic neuropathy showed T2-weighted magnetic resonance imaging high signal intensity in the posterior columns of the cervical spine. T2 changes reflected the degeneration of central sensory projections and localized the disease process to T-shaped dorsal root ganglion neurons. No similar abnormalities were found in sensory and sensorimotor length-dependent axonal neuropathy patients. Spinal cord magnetic resonance imaging is a useful tool to support the clinical diagnosis of primary ganglionopathy.

Cognitive and magnetic resonance imaging aspects of corticobasal degeneration and progressive supranuclear palsy

OBJECTIVE

To identify cognitive and MRI features important for the clinical diagnosis of corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP); these diseases share several clinical features and are often difficult to distinguish on clinical grounds.

METHODS

Cognitive functions and MRI characteristics were examined in 16 patients with CBD and 28 patients with PSP, all diagnosed according to current clinical criteria (none was examined by autopsy).

RESULTS

MRI findings differed significantly between the two groups: 87.5% of patients with CBD but none with PSP had asymmetric frontoparietal atrophy, whereas 89.3% of patients with PSP but only 6.3% of those with CBD had midbrain atrophy. Cognitive examination showed that ideomotor apraxia (De Renzi's test) was significantly more frequent in CBD, and executive functions (Nelson's test) were significantly more impaired in patients with PSP.

CONCLUSIONS

MRI findings of asymmetric frontoparietal atrophy in CBD and midbrain atrophy in PSP are the most consistent and useful aids to careful clinical evaluation for differentiating between the two diseases.

Frontotemporal dementia and corticobasal degeneration in a family with a P301S mutation in tau

The tau gene has been found to be the locus of dementia with rigidity linked to chromosome 17. Exonic and intronic mutations have been described in a number of families. Here we describe a P301S mutation in exon 10 of the tau gene in a new family. Two members of this family were affected. One individual presented with frontotemporal dementia, whereas his son has corticobasal degeneration, demonstrating that the same primary gene defect in tau can lead to 2 distinct clinical phenotypes. Both individuals developed rapidly progressive disease in the third decade. Neuropathologically, the father presented with an extensive filamentous pathology made of hyperphosphorylated tau protein. Biochemically, recombinant tau protein with the P301S mutation showed a greatly reduced ability to promote microtubule assembly.

Hemiballism in a patient with probable multiple system atrophy

We report a patient with long-standing asymmetrical parkinsonism, cerebellar ataxia and dysautonomia, suggestive of multiple system atrophy (MSA). However, the patient also developed involuntary repetitive movements similar to ballic dyskinesias and mental deterioration. MRI revealed major involvement of both posterior fossa structures and basal ganglia. The case would be accommodated within a rubric of MSA widened to include involvement of the subthalamic nucleus and the medial part of the pallidum, pathology which may account for the ballic movements. Additionally the patient's cognitive and behavioural disturbances suggest an impairment of striato-prefrontal cortex loop.

Acquired hemidystonia in childhood: a clinical and neuroradiological study of thirteen patients

A retrospective study of 13 patients (4 males/9 females) with acquired hemidystonia in childhood is reported. The mean age of onset of hemidystonia was 6.4 years (range 1-13.4 years); the mean duration of dystonia at the time of last follow-up was 11.4 years (range 3.6-23 years). Hemidystonia was caused by ischemic infarction in 9 patients and was attributed to perinatal trauma in 1; in 4 of the 9 patients with stroke and in the remaining 3 patients laboratory investigations were suggestive of primary antiphospholipid syndrome. Eleven of the 13 patients had delayed onset of dystonia: between 1 month and 8.9 years (mean 3.4 years). Ten patients had neuroradiological evidence of contralateral basal ganglia damage. A history of hemiparesis and evidence of striatal damage on CT or MRI were important risk factors for the development of dystonia. Response to medical treatment (trihexyphenidyl dose as high as 40 mg daily) in 5 patients was disappointing; 4 of the 5 patients who underwent functional stereotaxic operations were improved, but dystonia was still present at the end of the follow-up. Our study provides additional evidence that lesions of the striatum may induce dystonia, supporting the theory of striatopallido-thalamic disconnection. Furthermore, our results indicate that the occurrence of delayed dystonia must be considered in the diagnostic approach to childhood-onset dystonia.

Magnetic resonance signal abnormalities along the pyramidal tracts in amyotrophic lateral sclerosis

Magnetic resonance imaging (MRI) studies of the brain were reviewed in 16 patients with amyotrophic lateral sclerosis (ALS), representative of a large and homogeneously studied series, 11 of whom showed signal abnormalities along the pyramidal tracts. These were more frequent in patients with more severe upper motor neuron signs but did not correlate with disease severity. Our study suggests that MRI signal abnormalities along the pyramidal tracts are common in ALS and may reflect the severity of pyramidal tract degeneration.

Triventricular hydrocephalus: review of 71 cases evaluated at the Istituto Neurologico "C. Besta" Milan over the last 10 years

The authors review 71 patients with triventricular hydrocephalus in whom a contrast-enhanced CT scan did not show any tumoral or vascular lesion that could have caused the hydrocephalus. The patients were subdivided into three age groups. The results of the neuroradiological examination, the surgical treatment, and the complications of the shunt procedure are analyzed, with special reference to the high number (13) of periaqueductal alterations of signal pattern found on MRI (interpreted as a "slow growing" neoplasm) and to the incidence and causes of shunt malfunction.

Neurologic symptoms after epidural anaesthesia. Report of three cases

We describe 3 patients, who exhibited neurological symptoms after single dose epidural anaesthesia. In patient 1 an unrecognized spinal arteriovenous fistula (AVF) caused paraparesis following epidural block. The dilated veins draining an AVF are space-occupying structures and the injection of the anaesthetic solution may have precipitated latent ischaemic hypoxia of the spinal cord due to raised venous pressure. In patient 2, epidural block was followed by postoperative permanent saddle pain and hypoaesthesia. The injection of the anaesthetic in a narrow spinal canal with multiple discal protrusions and restriction of interlaminar foramina may have acutely produced mechanical compression of the spinal cord or roots. Patient 3 exhibited post-epidural block spinal arachnoiditis. Although the few reported cases of this syndrome exhibit severe neurological damage, our patient presented with scarse symptoms. Our cases point out the importance of accurate neurological history and examination of candidates for epidural anaesthesia and of accurate anaesthetic history for neurological patients.

Superficial siderosis of the CNS: MR diagnosis and clinical findings

PURPOSE

To report the clinical and neuroradiologic findings of superficial siderosis of the CNS, due to chronic subarachnoid bleeding of unknown origin.

MATERIALS AND METHODS

We observed seven cases. The main clinical manifestations were progressive deafness and ataxia. Four patients had had previous cranial or cervical trauma, with root avulsion in two, many years before onset of deafness and ataxia. Neuroradiologic studies included MR (0.5 T in four and 1.5 T in three) and angiography of the brain in all cases, CT in six cases, MR of the spine in six, and myelography in four.

RESULTS

MR demonstrated a rim of marked hypointensity in T2-weighted images, consistent with hemosiderin deposits, on the surface of cerebellum, brain stem, inferior part of cerebral hemispheres, and spinal cord. CT showed cerebellar atrophy in five cases, and a rim of mild hyperdensity around the brain stem in two. Angiographic studies were negative. Myelography showed cervical nerve root avulsion in two cases and a cervicodorsal extradural cyst in one. Cerebrospinal fluid contained RBCs in all the six examined cases.

CONCLUSION

Although CT may occasionally suggest the diagnosis of superficial siderosis, MR demonstrates this abnormality to better advantage.

The effects of wallerian degeneration of the optic radiations demonstrated by MRI

The effects of wallerian degeneration can be demonstrated by MRI as abnormal signal along the course of the degenerate fibres; they have previously been reported in the corticospinal tract. We report two cases of wallerian degeneration of the right optic radiations due to lesions of the right lateral geniculate body. The anatomy and the MRI visibility of the normal optic radiations are briefly discussed.

Hemifacial spasm in a child

Hemifacial spasm in a 10-year-old child is herein reported. Computed tomography and angiography were normal. Magnetic resonance imaging showed an anomalous vascular structure, probably a redundant loop arising from AICA or PICA, which was identified at surgery. The spasm, presumably due to vascular compression at the root entry zone of the right facial nerve, promptly and completely remitted after surgical decompression, without functional deficits. Atypical clinical features, as well as pre- and postoperative neurophysiological findings supporting the microvascular compression theory, are discussed.

Olivopontocerebellar atrophy: MR diagnosis and relationship to multisystem atrophy

Clinical diagnosis of olivopontocerebellar atrophy (OPCA) must be confirmed by radiologic demonstration of atrophy in an appropriate distribution. OPCA may be associated with degeneration of other systems in multisystem atrophy (MSA). The authors report 23 cases of OPCA, eight of which were associated with MSA. Atrophy involved the cerebellum, pons, and middle cerebellar peduncles in all cases. On intermediate and T2-weighted magnetic resonance (MR) images, abnormal signal intensity was always observed in the transverse pontine fibers, middle cerebellar peduncles, and cerebellum, structures known from pathologic study to degenerate in OPCA. Pyramidal tracts and superior cerebellar peduncles stood out because of their normal signal intensity. Of the eight patients with MSA, four also had variable abnormal signal intensities in the putamen. The authors believe that the combination of atrophy and abnormal signal intensity in the appropriate distribution strongly supports the diagnosis of OPCA. In some cases, MR imaging may demonstrate involvement of different systems, thus confirming the diagnosis of MSA.

Technical basis for magnetic resonance images

The spin-echo procedure is the basic technique in a magnetic resonance (MR) study (the magnetization vector is flipped by 90 degrees onto the ortogonal plane to the main magnetic field). Very soon after the MR procedure was developed, it was pointed out how important it is to achieve the needed contrast with shorter repetition times (TRs) to reduce the imaging time. Recently, fast imaging techniques have been introduced (partial flip angles, short TRs, and the lack of 180 degrees radiofrequency pulses to refocus the spins are their main characteristics; the spins are refocused by the application of a gradient reversal technique). These techniques are particularly needed in pediatric neuroradiology, where the examination time must be as short as possible. At present, partial flip-angle techniques are almost completely replacing the conventional spin-echo procedure, but the variations in flip angle could result in a change in contrast. For these reasons, conventional spin-echo techniques may still be useful in a routine MR study.

[Magnetic resonance in brain tumors: a classification based on signal behavior in multiple echo sequences]

MR is generally known to be more sensitive but less specific than CT in the detection of brain lesions. In our opinion multiple echo sequences can markedly improve MR specificity in the diagnosis of tumors. We reviewed a series of 343 intracranial tumors studied with MR using multiple echo sequences and histologically verified. On the basis of the different signal patterns we divided brain tumors into 5 classes. Class 1: the signal intensity of the tumor increases progressively in T2 WI (100% of craniopharyngiomas, 21/21; 100% of epidermoid tumors, 12/12; 81% of astrocytomas (grades I to III), 64/79; 65% of neurinomas, 30/46). Class 2: the signal intensity of the lesion decreases progressively in T2 WI: A) the tumor has higher signal intensity than the parenchyma in all echoes (100% of medulloblastomas, 14/14; 53% of pituitary adenomas, 15/28); B) the tumor has the same signal intensity as the parenchyma in late echo acquisitions (100% of ependymal tumors, 12/12; 60% of meningiomas, 25/41). Class 3: the tumor has the same signal intensity as the parenchyma in all echoes (34% of meningiomas, 14/41). Class 4: glioblastoma model: one or more cysts of high signal intensity in T2 WI and slightly hyperintense nodules and/or rings and hyperintense peritumoral edema (73% of glioblastomas, 35/48; 72% of metastases, 18/25). Class 5: oligodendroglioma model: mixed hyper/hypointense pattern; cyst, calcifications and edema are very difficult to recognize within the lesion (95% of oligodendrogliomas, 18/19). The signal pattern was sometimes characteristic but never pathognomonic. Nevertheless, this classification proved to be an useful criterion to restrict the number of possible diagnoses. The study of T1 and T2 values seems to be less useful.

MRI in internal carotid artery dissection

We report two cases of internal carotid artery dissection in which MRI unequivocally demonstrated the intramural hematoma. We propose that, whenever the clinical presentation or the angiogram suggest arterial dissection, MRI be done to confirm the diagnosis.

Problems and perspectives of diagnostic imaging: the pineal region

In 1970 the state of the art in neuroradiological diagnosis was considered satisfactory enough, if not almost perfect, by the people working in this field. But when a few years later Computerized Tomography appeared, a new impressive standard in neuroradiological resolution was achieved, moreover with a non-invasive method. In the '80 further improvement was brought by several striking new diagnostic technologies, such as Magnetic Resonance, Positron Emission Tomography and Single Photon Emission Computed Tomography which allow the physician to achieve a new standard in non-invasive high resolution neuro-imaging which was simply unbelievable a few years ago. A new era is now beginning in the neuro-radiological sciences in which the new techniques surely allow the diagnosis towards disease previously escaping the neuro-radiological observation.