Diagnostic Accuracy of Arterial Spin-Labeling, Dynamic Contrast-Enhanced, and DSC Perfusion Imaging in the Diagnosis of Recurrent High-Grade Gliomas: A Prospective Study.

BACKGROUND AND PURPOSE: For patients with high-grade gliomas, the appearance of a new, enhancing lesion after surgery and chemoradiation represents a diagnostic dilemma. We hypothesized that MR perfusion without and with contrast can differentiate tumor recurrence from radiation necrosis. MATERIALS AND METHODS: In this prospective study, we performed 3 MR perfusion methods: arterial spin-labeling, DSC, and dynamic contrast enhancement. For each lesion, we measured CBF from arterial spin-labeling, uncorrected relative CBV, and leakage-corrected relative CBV from DSC imaging. The volume transfer constant and plasma volume were obtained from dynamic contrast-enhanced imaging without and with T1 mapping using modified Look-Locker inversion recovery (MOLLI). The diagnosis of tumor recurrence or radiation necrosis was determined by either histopathology for patients who underwent re-resection or radiologic follow-up for patients who did not have re-resection. RESULTS: There were 26 patients with 32 lesions, 19 lesions with tumor recurrence and 13 lesions with radiation necrosis. Compared with radiation necrosis, lesions with tumor recurrence had higher CBF (P = .033), leakage-corrected relative CBV (P = .048), and plasma volume using MOLLI T1 mapping (P = .012). For differentiating tumor recurrence from radiation necrosis, the areas under the curve were 0.81 for CBF, 0.80 for plasma volume using MOLLI T1 mapping, and 0.71 for leakage-corrected relative CBV. A correlation was found between CBF and leakage-corrected relative CBV (r s = 0.54), volume transfer constant, and plasma volume (0.50 < r s< 0.77) but not with uncorrected relative CBV (r s = 0.20, P = .29). CONCLUSIONS: In the differentiation of tumor recurrence from radiation necrosis in a newly enhancing lesion, the diagnostic value of arterial spin-labeling-derived CBF is similar to that of DSC and dynamic contrast-enhancement-derived blood volume.

Stent-assisted coiling of posterior inferior cerebellar artery aneurysm complicated by arterial avulsion.

BACKGROUND: Rapid development of new devices and techniques in endovascular neurosurgery allows treatment of complex intracranial vascular lesions. These treatments, however, are not without risk. We report a case of unusual vascular laceration during stent-assisted coiling of a posterior inferior cerebellar artery (PICA) aneurysm. CASE PRESENTATION: A 75-year-old female with a recurrent, previously coiled PICA aneurysm developed avulsion of the parent vessel followed by fatal bleeding while an attempt was made to place a microcatheter across the aneurysmal neck for stent-assisted coiling. CONCLUSIONS: Pathological examination was performed to understand the mechanism of the rupture. The most likely mechanism was straightening of the significant vascular tortuosity, excessive tension on the vessel origin and avulsion upon advancement of the microcatheter over the microguidewire.

Diagnostic Accuracy of Centrally Restricted Diffusion in the Differentiation of Treatment-Related Necrosis from Tumor Recurrence in High-Grade Gliomas.

BACKGROUND AND PURPOSE: Centrally restricted diffusion has been demonstrated in recurrent high-grade gliomas treated with bevacizumab. Our purpose was to assess the accuracy of centrally restricted diffusion in the diagnosis of radiation necrosis in high-grade gliomas not treated with bevacizumab. MATERIALS AND METHODS: In this prospective study, we enrolled patients with high-grade gliomas who developed a new ring-enhancing necrotic lesion and who underwent re-resection. The presence of a centrally restricted diffusion within the ring-enhancing lesion was assessed visually on diffusion trace images and by ADC measurements on 3T preoperative diffusion tensor examination. The percentage of tumor recurrence and radiation necrosis in each surgical specimen was defined histopathologically. The association between centrally restricted diffusion and radiation necrosis was assessed using the Fisher exact test. Differences in ADC and the ADC ratio between the groups were assessed via the Mann-Whitney U test, and receiver operating characteristic curve analysis was performed. RESULTS: Seventeen patients had re-resected ring-enhancing lesions: 8 cases of radiation necrosis and 9 cases of tumor recurrence. There was significant association between centrally restricted diffusion by visual assessment and radiation necrosis (P = .015) with a sensitivity of 75% and a specificity of 88.9%, a positive predictive value 85.7%, and a negative predictive value of 80% for the diagnosis of radiation necrosis. There was a statistically significant difference in the ADC and ADC ratio between radiation necrosis and tumor recurrence (P = .027). CONCLUSIONS: The presence of centrally restricted diffusion in a new ring-enhancing lesion might indicate radiation necrosis rather than tumor recurrence in high-grade gliomas previously treated with standard chemoradiation without bevacizumab.

Correlation of Tumor Immunohistochemistry with Dynamic Contrast-Enhanced and DSC-MRI Parameters in Patients with Gliomas.

BACKGROUND AND PURPOSE: Tumor CBV is a prognostic and predictive marker for patients with gliomas. Tumor CBV can be measured noninvasively with different MR imaging techniques; however, it is not clear which of these techniques most closely reflects histologically-measured tumor CBV. Our aim was to investigate the correlations between dynamic contrast-enhanced and DSC-MR imaging parameters and immunohistochemistry in patients with gliomas. MATERIALS AND METHODS: Forty-three patients with a new diagnosis of glioma underwent a preoperative MR imaging examination with dynamic contrast-enhanced and DSC sequences. Unnormalized and normalized cerebral blood volume was obtained from DSC MR imaging. Two sets of plasma volume and volume transfer constant maps were obtained from dynamic contrast-enhanced MR imaging. Plasma volume obtained from the phase-derived vascular input function and bookend T1 mapping (Vp_Φ) and volume transfer constant obtained from phase-derived vascular input function and bookend T1 mapping (Ktrans_Φ) were determined. Plasma volume obtained from magnitude-derived vascular input function (Vp_SI) and volume transfer constant obtained from magnitude-derived vascular input function (Ktrans_SI) were acquired, without T1 mapping. Using CD34 staining, we measured microvessel density and microvessel area within 3 representative areas of the resected tumor specimen. The Mann-Whitney U test was used to test for differences according to grade and degree of enhancement. The Spearman correlation was performed to determine the relationship between dynamic contrast-enhanced and DSC parameters and histopathologic measurements. RESULTS: Microvessel area, microvessel density, dynamic contrast-enhanced, and DSC-MR imaging parameters varied according to the grade and degree of enhancement (P < .05). A strong correlation was found between microvessel area and Vp_Φ and between microvessel area and unnormalized blood volume (rs ≥ 0.61). A moderate correlation was found between microvessel area and normalized blood volume, microvessel area and Vp_SI, microvessel area and Ktrans_Φ, microvessel area and Ktrans_SI, microvessel density and Vp_Φ, microvessel density and unnormalized blood volume, and microvessel density and normalized blood volume (0.44 ≤ rs ≤ 0.57). A weaker correlation was found between microvessel density and Ktrans_Φ and between microvessel density and Ktrans_SI (rs ≤ 0.41). CONCLUSIONS: With dynamic contrast-enhanced MR imaging, use of a phase-derived vascular input function and bookend T1 mapping improves the correlation between immunohistochemistry and plasma volume, but not between immunohistochemistry and the volume transfer constant. With DSC-MR imaging, normalization of tumor CBV could decrease the correlation with microvessel area.

Isolated brain metastases as first site of recurrence in prostate cancer: case report and review of the literature.

Fewer than 2% of patients with metastatic prostate cancer (pca) develop brain metastases. Autopsy series have confirmed the rarity of brain metastases. When present, brain metastases occur in end stage, once the pca is castrate-resistant and spread to other sites is extensive. Here, we present a rare case of a patient with pca who developed a solitary parenchymal brain metastasis as first site of relapse 9 years after radical therapy. The patient underwent craniotomy and excision of the tumour. A second recurrence was also isolated to the brain. In the literature, pca patients with brain metastases have a poor mean survival of 1-7.6 months. The patient in our case report experienced a relatively favourable outcome, surviving 19 months after his initial brain relapse.

Comparison of the Diagnostic Accuracy of DSC- and Dynamic Contrast-Enhanced MRI in the Preoperative Grading of Astrocytomas.

BACKGROUND AND PURPOSE: Dynamic contrast-enhanced MR imaging parameters can be biased by poor measurement of the vascular input function. We have compared the diagnostic accuracy of dynamic contrast-enhanced MR imaging by using a phase-derived vascular input function and "bookend" T1 measurements with DSC MR imaging for preoperative grading of astrocytomas. MATERIALS AND METHODS: This prospective study included 48 patients with a new pathologic diagnosis of an astrocytoma. Preoperative MR imaging was performed at 3T, which included 2 injections of 5-mL gadobutrol for dynamic contrast-enhanced and DSC MR imaging. During dynamic contrast-enhanced MR imaging, both magnitude and phase images were acquired to estimate plasma volume obtained from phase-derived vascular input function (Vp_Φ) and volume transfer constant obtained from phase-derived vascular input function (K(trans)_Φ) as well as plasma volume obtained from magnitude-derived vascular input function (Vp_SI) and volume transfer constant obtained from magnitude-derived vascular input function (K(trans)_SI). From DSC MR imaging, corrected relative CBV was computed. Four ROIs were placed over the solid part of the tumor, and the highest value among the ROIs was recorded. A Mann-Whitney U test was used to test for difference between grades. Diagnostic accuracy was assessed by using receiver operating characteristic analysis. RESULTS: Vp_ Φ and K(trans)_Φ values were lower for grade II compared with grade III astrocytomas (P < .05). Vp_SI and K(trans)_SI were not significantly different between grade II and grade III astrocytomas (P = .08-0.15). Relative CBV and dynamic contrast-enhanced MR imaging parameters except for K(trans)_SI were lower for grade III compared with grade IV (P ≤ .05). In differentiating low- and high-grade astrocytomas, we found no statistically significant difference in diagnostic accuracy between relative CBV and dynamic contrast-enhanced MR imaging parameters. CONCLUSIONS: In the preoperative grading of astrocytomas, the diagnostic accuracy of dynamic contrast-enhanced MR imaging parameters is similar to that of relative CBV.

LIMS2 mutations are associated with a novel muscular dystrophy, severe cardiomyopathy and triangular tongues.

Limb girdle muscular dystrophy (LGMD) is a heterogeneous group of genetic disorders leading to progressive muscle degeneration and often associated with cardiac complications. We present two adult siblings with childhood-onset of weakness progressing to a severe quadriparesis with the additional features of triangular tongues and biventricular cardiac dysfunction. Whole exome sequencing identified compound heterozygous missense mutations that are predicted to be pathogenic in LIMS2. Biopsy of skeletal muscle demonstrated disrupted immunostaining of LIMS2. This is the first report of mutations in LIMS2 and resulting disruption of the integrin linked kinase (ILK)-LIMS-parvin complex associated with LGMD.

Preoperative prognostic value of dynamic contrast-enhanced MRI-derived contrast transfer coefficient and plasma volume in patients with cerebral gliomas.

BACKGROUND AND PURPOSE: The prognostic value of dynamic contrast-enhanced MR imaging-derived plasma volume obtained in tumor and the contrast transfer coefficient has not been well-established in patients with gliomas. We determined whether plasma volume and contrast transfer coefficient in tumor correlated with survival in patients with gliomas in addition to other factors such as age, type of surgery, preoperative Karnofsky score, contrast enhancement, and histopathologic grade. MATERIALS AND METHODS: This prospective study included 46 patients with a new pathologically confirmed diagnosis of glioma. The contrast transfer coefficient and plasma volume obtained in tumor maps were calculated directly from the signal-intensity curve without T1 measurements, and values were obtained from multiple small ROIs placed within tumors. Survival curve analysis was performed by dichotomizing patients into groups of high and low contrast transfer coefficient and plasma volume. Univariate analysis was performed by using dynamic contrast-enhanced parameters and clinical factors. Factors that were significant on univariate analysis were entered into multivariate analysis. RESULTS: For all patients with gliomas, survival was worse for groups of patients with high contrast transfer coefficient and plasma volume obtained in tumor (P < .05). In subgroups of high- and low-grade gliomas, survival was worse for groups of patients with high contrast transfer coefficient and plasma volume obtained in tumor (P < .05). Univariate analysis showed that factors associated with lower survival were age older than 50 years, low Karnofsky score, biopsy-only versus resection, marked contrast enhancement versus no/mild enhancement, high contrast transfer coefficient, and high plasma volume obtained in tumor (P < .05). In multivariate analysis, a low Karnofsky score, biopsy versus resection in combination with marked contrast enhancement, and a high contrast transfer coefficient were associated with lower survival rates (P < .05). CONCLUSIONS: In patients with glioma, those with a high contrast transfer coefficient have lower survival than those with low parameters.

Diagnostic accuracy of dynamic contrast-enhanced MR imaging using a phase-derived vascular input function in the preoperative grading of gliomas.

BACKGROUND AND PURPOSE: The accuracy of tumor plasma volume and K(trans) estimates obtained with DCE MR imaging may have inaccuracies introduced by a poor estimation of the VIF. In this study, we evaluated the diagnostic accuracy of a novel technique by using a phase-derived VIF and "bookend" T1 measurements in the preoperative grading of patients with suspected gliomas. MATERIALS AND METHODS: This prospective study included 46 patients with a new pathologically confirmed diagnosis of glioma. Both magnitude and phase images were acquired during DCE MR imaging for estimates of K(trans)_φ and V(p_)φ (calculated from a phase-derived VIF and bookend T1 measurements) as well as K(trans)_SI and V(p_)SI (calculated from a magnitude-derived VIF without T1 measurements). RESULTS: Median K(trans)_φ values were 0.0041 minutes(-1) (95 CI, 0.00062-0.033), 0.031 minutes(-1) (0.011-0.150), and 0.088 minutes(-1) (0.069-0.110) for grade II, III, and IV gliomas, respectively (P ≤ .05 for each). Median V(p_)φ values were 0.64 mL/100 g (0.06-1.40), 0.98 mL/100 g (0.34-2.20), and 2.16 mL/100 g (1.8-3.1) with P = .15 between grade II and III gliomas and P = .015 between grade III and IV gliomas. In differentiating low-grade from high-grade gliomas, AUCs for K(trans)_φ, V(p_φ), K(trans)_SI, and V(p_)SI were 0.87 (0.73-1), 0.84 (0.69-0.98), 0.81 (0.59-1), and 0.84 (0.66-0.91). The differences between the AUCs were not statistically significant. CONCLUSIONS: K(trans)_φ and V(p_)φ are parameters that can help in differentiating low-grade from high-grade gliomas.

Abnormalities of the nucleus and nuclear inclusions in neurodegenerative disease: a work in progress.

Neurodegenerative diseases are characterized pathologically by the abnormal accumulation of pathogenic protein species within the cell. Several neurodegenerative diseases feature intranuclear protein aggregation in the form of intranuclear inclusion bodies. Studies of these intranuclear inclusions are providing important clues regarding the cellular pathophysiology of these diseases, as exemplified by recent progress in defining the genetic basis of a subset of frontotemporal dementia cases. The precise role of intranuclear inclusion bodies in disease pathogenesis is currently a focus of debate. The present review provides an overview of the diverse family of neurodegenerative diseases in which nuclear inclusions form part of the neuropathological spectrum. In addition, current pathogenetic concepts relevant to these diseases will be reviewed and arguments for and against a protective role for intranuclear inclusions will be presented. The relationship of pathological intranuclear inclusions to functional intranuclear bodies will also be discussed. Finally, by analogy with pathological intranuclear inclusions, I will speculate on the possibility that intranuclear protein aggregation may represent a constitutive cellular protective mechanism occurring in neurons under physiological conditions.

Promyelocytic leukaemia-immunoreactive neuronal intranuclear rodlets in the human brain.

In a previous study, we demonstrated immunoreactivity of a subset of neuronal intranuclear rodlets (INRs) in the human substantia nigra for promyelocytic leukaemia (PML) protein, the signature protein of PML bodies. In the present study, we extend these observations and describe the ultrastructural features, immunohistochemical staining characteristics, and topographical pattern of distribution of PML-immunoreactive intranuclear rodlets (PML-INRs). Consistent with a purported role for PML bodies in nuclear proteolysis and/or transcriptional regulation, PML-INRs are immunoreactive for components of the ubiquitin-proteasome system, the transcriptional regulator CREB-binding protein, acetylated histone H4, and the eukaryotic translation initiation factor eIF4E. Immunoelectron microscopy reveals that they all possess a filamentous core and, in some, this is surrounded by a granular shell. We further demonstrate that a proportion of INRs in extranigral sites also show partial immunoreactivity for PML. These observations indicate an intimate association between two neuronal nuclear bodies, PML bodies and INRs. Because both of these structures have been implicated in neurodegenerative disease, PML-INRs may provide a tool with which to study changes in nuclear substructure in disease.

Delayed spinocerebellar ataxia in transgenic mice expressing mutant ubiquitin.

Spinocerebellar ataxia type 1 (SCA1) is an incurable neurodegenerative disease resulting from loss of Purkinje neurones within the cerebellum. The ubiquitin proteasome pathway (UPP) has been implicated in SCA1 but the role of proteolysis in the disease is still poorly understood. To further investigate this issue in vivo, genetic crosses were performed between an established mouse model of SCA1 and novel strains expressing elevated levels of wild type or mutant isoforms of ubiquitin. The K48R mutant isoform of ubiquitin (a dominant negative inhibitor of proteolysis) was found to significantly delay the deterioration of Purkinje neurones as evidenced by behavioural, morphological, and molecular indicators. This delay was accompanied by stabilization of p300/CBP, transcriptional mediators whose abundance and activity would otherwise decline in the course of the SCA1 disease, and persistence of protein kinase C gamma (PKCgamma), a protein involved in Purkinje cell dendritic development that is mutated in one form of spinocerebellar ataxia. Whereas the stabilization of p300/CBP was found to occur at the post-translational level the modulation of PKCgamma was at the level of transcription. These results are consistent with transcriptional dysregulation as a key mechanism in neurodegeneration through loss of p300/CBP. Further, the results suggest that the UPP is a potentially useful target for the development of novel therapies for the treatment of neurodegenerative disease.

NMDA receptors mediate calcium accumulation in myelin during chemical ischaemia.

Central nervous system myelin is a specialized structure produced by oligodendrocytes that ensheaths axons, allowing rapid and efficient saltatory conduction of action potentials. Many disorders promote damage to and eventual loss of the myelin sheath, which often results in significant neurological morbidity. However, little is known about the fundamental mechanisms that initiate myelin damage, with the assumption being that its fate follows that of the parent oligodendrocyte. Here we show that NMDA (N-methyl-d-aspartate) glutamate receptors mediate Ca2+ accumulation in central myelin in response to chemical ischaemia in vitro. Using two-photon microscopy, we imaged fluorescence of the Ca2+ indicator X-rhod-1 loaded into oligodendrocytes and the cytoplasmic compartment of the myelin sheath in adult rat optic nerves. The AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid)/kainate receptor antagonist NBQX completely blocked the ischaemic Ca2+ increase in oligodendroglial cell bodies, but only modestly reduced the Ca2+ increase in myelin. In contrast, the Ca2+ increase in myelin was abolished by broad-spectrum NMDA receptor antagonists (MK-801, 7-chlorokynurenic acid, d-AP5), but not by more selective blockers of NR2A and NR2B subunit-containing receptors (NVP-AAM077 and ifenprodil). In vitro ischaemia causes ultrastructural damage to both axon cylinders and myelin. NMDA receptor antagonism greatly reduced the damage to myelin. NR1, NR2 and NR3 subunits were detected in myelin by immunohistochemistry and immunoprecipitation, indicating that all necessary subunits are present for the formation of functional NMDA receptors. Our data show that the mature myelin sheath can respond independently to injurious stimuli. Given that axons are known to release glutamate, our finding that the Ca2+ increase was mediated in large part by activation of myelinic NMDA receptors suggests a new mechanism of axo-myelinic signalling. Such a mechanism may represent a potentially important therapeutic target in disorders in which demyelination is a prominent feature, such as multiple sclerosis, neurotrauma, infections (for example, HIV encephalomyelopathy) and aspects of ischaemic brain injury.

Protective effects of mutant ubiquitin in transgenic mice.

The K48R mutant ubiquitin can exert profound in vivo protective effects against a variety of insults, including agents of direct clinical relevance. The manipulation of the ubiquitin/proteasome pathway has enormous potential for clinical benefit, and it is not unreasonable to expect that such benefits will include diseases of aging.

Frontotemporal dementia with ubiquitinated cytoplasmic and intranuclear inclusions.

Dementia of motor neuron disease type (DMND) is a variety of frontotemporal dementia (FTD) which is pathologically defined by characteristic neuronal ubiquitinated, tau- and synuclein-negative intracytoplasmic inclusions. Many cases with this pathology, however, do not have motor neuron disease. In the present study, we document the presence of ubiquitinated neuronal intranuclear inclusions in a sub-population of cases of neuropathologically verified DMND. Immunohistochemical localization of ubiquitin was performed on sections of post-mortem brain from 12 patients with DMND as well as from cases with other neurodegenerative diseases including amyotrophic lateral sclerosis, Parkinson's disease, dementia with Lewy bodies, corticobasal degeneration, progressive supranuclear palsy, and multiple system atrophy. All of the cases of DMND showed ubiquitinated, tau-negative intracytoplasmic inclusions in dentate granule cells and cortical neurons. Of these 12 cases of DMND, 3 also showed neuronal ubiquitinated intranuclear inclusions. In 1 of these cases, CAG repeat expansions in the genes known to harbor these mutations were excluded. Cases with intranuclear inclusions displayed striatal atrophy and reduced brain weight relative to non-inclusion-bearing cases. In addition, patients with intranuclear inclusions tended to have a younger age of onset, a prolonged duration of disease, absence of motor neuron symptoms, and a family history of dementia. Intranuclear inclusions were not identified in the control cases with other neurodegenerative diseases. Ubiquitinated neuronal intranuclear inclusions have not been reported previously in DMND. The presence of ubiquitinated intranuclear inclusions along with striatal atrophy in a subset of cases of DMND may signify the existence of a neuropathologically distinct subset of this unique form of FTD.

Monoclonal antibodies against Epstein-Barr virus cross-react with alpha-synuclein in human brain.

Using antibodies generated against the latent membrane protein 1 of Epstein-Barr virus, intense immunoreactivity of Lewy bodies (in PD and dementia with Lewy bodies) and glial cytoplasmic inclusions (in multiple system atrophy) was demonstrated. ELISA and Western blotting techniques confirmed that this immunolabeling was due to cross-reactivity of the antiviral antibody with alpha-synuclein, a neuronal protein implicated in the pathogenesis of PD. This example of cross-reactivity between Epstein-Barr virus and alpha-synuclein may bear implications for further elucidating infectious or autoimmune mechanisms in PD.

Class III beta-tubulin immunoreactive intranuclear inclusions in human ependymomas and gangliogliomas.

We have observed intranuclear inclusion bodies immunoreactive for the cytoskeletal protein class III beta tubulin (C3betaT) in neurons and ependymal cells of post-mortem human brain. The relationship of these inclusions, detected by light microscopy, to the intranuclear rodlets described by the classical microscopists is unknown. The present study was conducted to determine whether these proteinaceous inclusions (C3betaT-NIIs) exist in the neoplastic counterparts of these cell types. Immunohistochemical staining for C3betaT revealed intensely stained, predominantly rod-shaped intranuclear inclusions in a variable proportion of tumor cells in five of ten ependymomas. In addition, C3betaT-NIIs were encountered in less than 1% of neuronal cells in two of five gangliogliomas. This study represents the first report of tubulin-containing intranuclear inclusions in brain tumors. The functional significance of these inclusions in normal human brain and in cerebral neuroepithelial neoplasms remains to be determined.

Tubulin immunoreactive neuronal intranuclear inclusions in the human brain.

Intranuclear filamentous and crystalline inclusion bodies have been described in the nuclei of a variety of cells in both normal and pathological states. The functional significance of these structures remains to be elucidated. Moreover, although the proteinaceous nature of these inclusions has been inferred in some histochemical studies, the identity of their constituent proteins remains to be determined. In the present study, immunohistochemistry was used to investigate the presence of intranuclear inclusions in neurones of the human brain which are intensely immunoreactive for the neuronal cytoskeletal protein class III beta tubulin. The ability to label these structures immunohistochemically was exploited to investigate the topographic pattern of distribution of these inclusions in the human brain. Intranuclear inclusions were rod-shaped, polygonal, or irregular in shape. They were present in neurones and ependymal cells. Intranuclear inclusion-bearing neurones were distributed in an anatomically heterogeneous pattern in the brain. Areas exhibiting relatively high densities of inclusions included the substantia inominata and anterior olfactory nucleus, dentate gyrus, substantia nigra, inferior olivary nucleus, and dentate nucleus of the cerebellum. In addition, intranuclear inclusions were prevalent in neurones in layers II, V, and VI of the cerebral cortex. They were particularly prevalent in the mesial basal temporal neocortex. The relationship of these structures to the intranuclear rods and sheets of the classical microscopists is uncertain. The demonstration that they are composed, at least in part, of tubulin, a major cytoskeletal protein, provides important clues regarding the mechanisms underlying their formation and provides a springboard for developing hypotheses regarding their functional significance. Furthermore, the ability to demonstrate these inclusions immunohistochemically provides an avenue for further studies directed at elucidating the potential involvement of these inclusions in various pathological settings.