Amyloid in neurosurgical and neurological practice.

The amyloidoses are a diverse group of diseases characterized by the deposition of specific proteins with distinct affinity to the dye Congo red, collectively called amyloid. The amyloidogenic proteins have acquired an abnormal, highly ordered, beta-pleated sheet configuration with a propensity to self-aggregate. The amyloid may be distributed in different organs with a remarkable diversity. Two broad categories of amyloidoses are recognised: The systemic (consisting of the primary or light chain form, the secondary or reactive form and the familial or hereditary form) and the localised that target specific organs. A tropism of amyloid proteins to the neural tissue produces certain patterns of central nervous system diseases: cerebral amyloid angiopathy, a substrate of spontaneous intracerebral haemorrhage; mature neuritic plaques found in Alzheimer disease and a subset of prion diseases; a topographically restricted accumulation of extracellular proteins giving rise to tumour-mimicking masses, the amyloidomas; and finally, spinal extradural amyloid collections that occasionally are found in the context of rheumatoid arthritis. In this review article we present original illustrative cases of amyloid diseases of the central nervous system that may be encountered in neurosurgical and neurological practice. Molecular aspects and clinical management problems are discussed.     

Hereditary cerebral amyloid angiopathies

Cerebral amyloid angiopathies are defined by the presence of amyloid substance in the walls of cerebral vessels. All amyloid substances have a particular physico-chemical structure, which imparts certain specific staining properties, but the biochemical composition of different amyloid types varies. Different forms of cerebral amyloid angiopathy have been identified, based on the biochemical nature of the protein deposited (e.g. beta-amyloid, cystatin C, transthyretin, gelsolin, amyloid protein Bri, prion protein). Some cerebral amyloid angiopathies are familial; these prompted genetic studies which in turn led to a better understanding of the genes coding for different amyloid proteins. As a group, cerebral amyloid angiopathies have certain neuropathological lesions in common. Infiltration by amyloid substance results in weakening of the small vessel walls and secondary complications responsible for changes such as microinfarcts and miliary haemorrhages in the cerebral cortex, lobar haemorrhages and/or leucoencephalopathy. These changes form the basis of the neurological complications: meningeal and cerebral haemorrhages, transient ischaemic episodes, vascular dementia. However each type of hereditary cerebral amyloid angiopathy has individual clinical and histopathological features reflecting the severity of arterial involvement, the extent of amyloid deposition within or outside the central nervous system, and the association with other neurodegenarative changes.     

Distribution of the protease inhibitor alpha 1-antichymotrypsin in cerebral and systemic amyloid.

We performed immunocytochemical staining to study the distribution of serum protease inhibitors in cerebral and systemic amyloid deposits. In beta-protein amyloid deposits in Alzheimer's disease, Down's syndrome, age-related cerebral amyloidosis, sporadic cerebral amyloid angiopathy and hereditary cerebral hemorrhage with amyloidosis of Dutch origin, antibody to alpha 1-antichymotrypsin (ACT) stains senile plaques and vascular deposits. Immature plaques or preamyloid deposits, identified by their positive staining for beta-protein and negative staining for Congo red, which represents the earliest recognizable stages of amyloid deposition, are also labeled. We did not detect ACT in other chemically different forms of cerebral and systemic amyloid. None of the other inhibitors in this study, i.e. antithrombin III and alpha 2-macroglobulin, was detected in the amyloid deposits. Neurons and glial cells throughout the central nervous system in normal and amyloid-containing brains also bind ACT antibody. The results emphasize the close association of ACT with one type of cerebral amyloid (beta-amyloid diseases) as well as the failure to detect such an association in other chemically different forms of cerebral and systemic amyloids.     

Progressive dementia, without cerebral hemorrhage, in a patient with hereditary cerebral amyloid angiopathy

A now 58-year-old female patient, carrier of the point-mutation in the β-amyloid gene on chromosome 21 which causes hereditary cerebral hemorrhage with amyloidosis — Dutch type, developed progressive dementia after the age of 55 years. She never suffered from a cerebral hemorrhage. Dementia has been described as a feature of hereditary amyloid angiopathy before, but only in patients who also suffer from strokes. The clinical manifestation of the patient described here underlines the relation between the Dutch type of hereditary amyloid angiopathy and (familial) Alzheimer's disease.     

Granulomatous angiitis and cerebral amyloid angiopathy presenting as a mass lesion.

A woman, who presented with clinical and radiological signs of a right temporal mass suggestive of a brain tumour, was found to have granulomatous angiitis associated with cerebral amyloid angiopathy; the diagnosis was confirmed by biopsy. She is still well 13 years after excision of the lesion. The association of granulomatous angiitis and cerebral amyloid angiopathy constitutes a peculiar variety of central nervous system micro-angiopathy. Only a few similar cases have been described.     

Morphological evaluation of amyloid-laden arteries in leptomeninges,cortices and subcortices in cerebral amyloid angiopathy with subcortical hemorrhage

To investigate the relationship between cerebral amyloid angiopathy and subcortical (lobar) hemorrhage, we examined the severity of amyloid deposition in the leptomeningeal, cortical and subcortical arteries in 28 autopsied elderly patients with cerebral amyloid angiopathy with subcortical hemorrhage, deep cerebral hemorrhage or without hemorrhage. The severity was evaluated in terms of the frequency of amyloid-laden arteries and the degree of amyloid deposition within the arteries. The frequency of amyloid-laden arteries, especially among arteries over 200 m in diameter, was higher in subcortical hemorrhage group than in the deep hemorrhage group and the non-hemorrhage group, and when the degree of amyloid deposition in the arteries was divided into four grades (none, mild, moderate or severe), the severity was higher in the subcortical hemorrhage group than in the deep cerebral hemorrhage group and the non-hemorrhage group. These results suggest that severe cerebral amyloid angiopathy is related to non-traumatic subcortical hemorrhage in elderly persons.     

Vascular amyloid in the aging central nervous system. Clinico-pathological study and literature review

The clinico-pathological features of five patients with vascular amyloid restricted to the central nervous system are presented. In three normotensive patients, intracerebral hemorrhage was the dramatic manifestation of amyloid angiopathy. In two other cases, one of amyloid in an arteriovenous malformation, the other of amyloid following therapeutic radiation, amyloid deposition was asymptomatic. Clinically, amyloid angiopathy must be considered in the different diagnosis of intracerebral hemorrhage, independent of the presence of dementia. Pathologically, a factor common to the syndrome of cerebrovascular amyloid appears to be locally increased vascular permeability resulting from a variety of previous tissue injuries.     

Gelsolin-related spinal and cerebral amyloid angiopathy

Gelsolin-related amyloidosis (familial amyloidosis, Finnish type) is a rare disorder, reported worldwide in kindreds carrying a G654A or G654T gelsolin gene mutation. Facial palsy, mild peripheral neuropathy, and corneal lattice dystrophy are characteristic, but atrophic bulbar palsy, ataxia of gait, and minor cognitive impairment may occur. In histological and immunohistochemical studies of the central nervous system in 4 patients with a G654A gelsolin mutation, we found widespread spinal, cerebral, and meningeal amyloid angiopathy, with deposition of gelsolin-related amyloid (AGel). Marked extravascular deposits occurred in the dura, spinal nerve roots, and sensory ganglia. The amyloid deposits were also variably immunoreactive for apolipoprotein E (ApoE), alpha1-antichymotrypsin (alpha1-ACT), and cystatin C (Cys C). Cerebral perivascular fibrinogen immunoreactivity was occasionally noted. The patients showed posterior column degeneration and diffuse loss of myelin in the centrum semiovale with perivascular accentuation. Postmortem magnetic resonance imaging, performed on 1 patient, showed white matter lesions, colocalizing with the histological abnormalities. Our study shows that deposition of AGel in the spinal and cerebral blood vessel walls, meninges, as well as spinal nerve roots and sensory ganglia is an essential feature of this form of systemic amyloidosis and may contribute to the central nervous system symptoms.     

Characterization of a transthyretin-related amyloid fibril protein from cerebral amyloid angiopathy in type I familial amyloid polyneuropathy.

Recently, it has been reported that transthyretin (TTR)-immunoreactive amyloid deposition with cerebral amyloid angiopathy in central nervous system is a common pathological finding in type I familial amyloid polyneuropathy (FAP). In the present study, we performed isolation and sequence analysis of TTR-related amyloid fibril protein from the meninges of a patient with type I FAP. Purified major amyloid fibril protein had a molecular weight of 15 kDa. Complete sequence analysis revealed that this amyloid fibril protein was a variant TTR with a single amino acid substitution of methionine for valine at position 30. This variant TTR is a previously unrecognized as cerebrovascular amyloid fibril protein. Furthermore, the patients with type I FAP are well known to have the variant TTR in the serum. These suggest that cerebrovascular amyloid fibril protein in type I FAP may derive from a serum precursor.     

Diagnosis of cerebral amyloid angiopathy by enzyme-linked immunosorbent assay of cystatin C in cerebrospinal fluid.

An abnormally low level of cystatin C in the cerebrospinal fluid is a diagnostic marker for the hereditary form of brain hemorrhage associated with amyloidosis that was first identified in Iceland. We developed an assay for cystatin C to use in the diagnosis of patients with cerebral amyloid angiopathy and brain hemorrhage. This test consists of a sandwich enzyme-linked immunosorbent assay using monoclonal mouse anticystatin C and polyclonal rabbit anticystatin C antibodies. The cystatin C level was assayed in cerebrospinal fluid samples from 29 patients with brain hemorrhage and 45 control patients with other neurological diseases. Fifteen patients with brain hemorrhage showed low cystatin C levels (less than or equal to 70 ng/ml) in a clinical setting in which the positive and negative findings were compatible with a diagnosis of cerebral amyloid angiopathy. Immunohistological examination of brain tissue obtained by biopsy from two of the 15 patients confirmed the diagnosis of cerebral amyloid angiopathy and identified the deposition of cystatin C and beta-protein. This enzyme-linked immunosorbent assay is simple to perform and may be useful for investigating patients suspected of having cerebral amyloid angiopathy with brain hemorrhage and the deposition of cystatin C.     

Co-localization of β/A4 and cystatin C in cortical blood vessels in Dutch, but not in Icelandic hereditary cerebral hemorrhage with amyloidosis

Based on the recent discovery of co-localization of β/A4 and cystatin C in cortical blood vessels of patients with cerebral hemorrhages due to sporadic amyloid angiopathy and patients with Alzheimer's disease we investigated the presence of these two proteins in the cortical blood vessels of patients suffering from hereditary cerebral hemorrhage with amyioidosis of the Dutch (n = 11) and the Icelandic (n = 2) type. The brains of three patients with sporadic cerebral amyloid angiopathy were also investigated. Blood vessels of the Dutch patients clearly showed immunostaining with β/A4 as well as with cystatin C antibodies, whereas the blood vessels of Icelandic patients showed only staining with cystatin C. In one of the three sporadic amyloid angiopathy patients co-localization was shown as well. The co-localization of mutated β/A4 with normal cystatin C in the Dutch patients suggests that cystatin C deposition occurs secondarily to β/A4 deposition. This is probably also the case in sporadic amyloid angiopathy and Alzheimer's disease. Cystatin C deposition may play a role in the development of cerebral hemorrhages and leukoencephalopathy.     

Cerebral amyloid angiopathies: a pathologic, biochemical, and genetic view

Amyloid deposition can take place in the walls of arteries, arterioles, and, less often, capillaries and veins of the central nervous system, a phenomenon known as cerebral amyloid angiopathy (CAA). The major clinicopathological manifestations of CAA include cerebral hemorrhage, ischemic lesions, and dementia. CAA may be classified according to the amyloid protein deposited. In the most common form, sporadic CAA, and in CAA related to sporadic Alzheimer disease (AD). A beta deposition is characteristic. CAA can also be severe in variants of familial AD caused by mutations of the amyloid-beta precursor protein or presenilin-1 genes in which deposition of A beta variants and/or wild-type A beta occurs. Other amyloid proteins involved in familial CAAs include 1) the mutant cystatin C (ACys) in hereditary cerebral hemorrhage with amyloidosis of Icelandic type, 2) variant transthyretins (ATTR) in meningo-vascular amyloidoses, 3) mutated gelsolin (AGel) in familial amyloidosis of Finnish type, 4) disease-associated prion protein (PrP(Sc)) in a variant of the Gerstmann-Str?ussler-Scheinker syndrome, and 5) ABri and ADan in CAAs observed in the recently described BRI2 gene-related dementias, familial British dementia and familial Danish dementia, respectively. This review addresses issues related to the correlation between morphology, biochemistry, and genetics, and briefly discusses both the pathogenesis and animal models of CAAs.     

Cerebral amyloid angiopathy presenting with vasculitic pathology.

We present an elderly patient with an unusual extensive multifocal central nervous system mass lesion, with dramatic imaging changes but only minor disturbance of cerebral function. Cerebral biopsy revealed an unexpected finding of severe cerebral amyloid angiopathy with secondary florid vasculitic appearances, which is a very rare but recognised association. Immunosuppression has produced significant sustained clinical and radiological remission.     

Familial British dementia (FBD): a cerebral amyloidosis with systemic amyloid deposition

Introduction:  FBD is an autosomal dominant disease with neuropathological similarities to Alzheimer's disease (AD) as it is characterized by amyloid angiopathy, parenchymal amyloid plaque deposition and neurofibrillary degeneration. FBD is associated with a stop codon mutation in the BRI2 gene encoding a type II transmembrane protein, BriPP. Mutation results in an extended precursor protein, ABriPP, from which a C-terminal 34 amino acid peptide (ABri) is generated by furin-like proteolytic cleavage and deposited as amyloid and preamyloid in the central nervous system. Despite the morphological parallels with AD the sequences of the amyloidogenic peptides, ABri in FBD and Aβ in AD, are completely different. We examined systemic tissues in FBD for ABri deposition.
Materials and methods:  Immunohistochemistry using an ABri-specific antibody, Ab338, counterstained with Thioflavin S and Ab338 immuno-electron microscopy identified ABri deposits and determined whether these were amyloid or preamyloid in nature.
Results:  Amyloid bearing blood vessels stained positively for ABri in myocardium, uterus, bladder, spleen, pancreas, lung and skeletal muscle. ABri was also identified in either amyloid or preamyloid conformation in the parenchyma of myocardium, adrenal, pancreas and skeletal muscle.
Conclusion:  This study demonstrates that FBD is the first described cerebral amyloidosis with neurofibrillary pathology and dementia to be accompanied by systemic amyloid deposition.     

Immunohistochemical characterization of cerebrovascular amyloid in 46 autopsied cases using antibodies to beta protein and cystatin C

Using immunohistochemical staining methods with antibodies to amyloid beta protein and human cystatin C, we examined cerebrovascular amyloid protein in the brains from 46 cases with cerebral amyloid angiopathy (seven with Alzheimer's disease, one with Down's syndrome, 18 with intracranial hemorrhage, 10 with cerebral infarction, and 10 elderly patients without any neurologic disorder). All cerebrovascular amyloid deposits in these 46 cases were consistently immunoreactive to anti-beta protein antibody. However, in nine cases some vascular walls with strong beta protein immunoreactivity also reacted less intensely with the anti-cystatin C antiserum. Of these nine cases, seven showed relatively heavy cerebrovascular amyloid deposition, and all seven had suffered a fatal subcortical hemorrhage presumably caused by cerebral amyloid angiopathy. Previous limited studies have suggested that the amyloid protein seen in elderly individuals with cerebral amyloid angiopathy is composed of beta protein. However, subcortical hemorrhage rarely occurs in such individuals. Our study shows that aged patients with different brain disorders commonly suffer from beta protein-type cerebral amyloid angiopathy, and we also suggest that the severity of beta protein-type cerebrovascular amyloid deposition is a fundamental factor in cerebral amyloid angiopathy-induced brain hemorrhage in the elderly. The nature of the cystatin C-immunoreactive substance in some of these vascular lesions is uncertain, but it might conceivably play an additional important role in the pathogenesis of brain hemorrhage in these cases.     

Human choroid plexus is an uniquely involved area of the brain in amyloidosis: a histochemical, immunohistochemical and ultrastructural study

To better understand the characteristics of amyloid deposition in the choroid plexus, we examined autopsied brain by routine histology, immunohistochemistry, and electron microscopy in three group of patients: primary systemic amyloidosis (n=7), cerebral amyloid angiopathy (CAA, n=6), and controls (n=3). Three of the CAA patients had Alzheimer's disease. Congophilic, birefringent amyloid deposits of the choroid plexus were seen in six of the seven cases of systemic light chain amyloidosis. Immunohistochemistry revealed that the deposited amyloids had reactivity for immunoglobulin light chain and amyloid P component. Accumulation of macrophages labeled with monoclonal antibodies against CD 68 and major histocompatibility complex class II antigens were observed around the massive amyloid deposits. The presence of approximately 10 nm amyloid fibrils along the epithelial basement membrane as well as in the vascular walls was ascertained by electron microscopy. In CAA, Congo red-positive amyloid deposits were consistently present in meningeal blood vessels and were often found in senile plaques of the cerebral parenchyma; congophilic amyloid deposits were absent in the choroid plexus. Choroid plexus epithelial cells exhibited immunostaining for beta amyloid precursor protein (APP) with N-terminal- and C-terminal-specific antibodies; in particular, consistent staining was obtained for the latter antibody. Immunoreactivity for amyloid β protein (Aβ) with monoclonal antibodies (6E10, 4G8) was often found in choroid plexus epithelial cells. These findings suggest that amyloid deposition of the choroid plexus depends on the major component protein in amyloidosis, and that the choroid plexus may produce APP and Aβ protein although Aβ amyloidosis is not evident in the choroid plexus. ©1997 Elsevier Science B.V. All rights reserved.     

Amyloid beta-peptide worsens cognitive impairment following cerebral ischemia-reperfusion injury

Amyloid β-peptide,a major component of senile plaques in Alzheimer’s disease,has been implicated in neuronal cell death and cognitive impairment.Recently,studies have shown that the pathogenesis of cerebral ischemia is closely linked with Alzheimer’s disease.In this study,a rat model of global cerebral ischemia-reperfusion injury was established via occlusion of four arteries;meanwhile,fibrillar amyloidβ-peptide was injected into the rat lateral ventricle.The Morris water maze test and histological staining revealed that administration of amyloidβ-peptide could further aggravate impairments to learning and memory and neuronal cell death in the hippocampus of rats subjected to cerebral ischemia-reperfusion injury.Western blot showed that phosphorylation of tau protein and the activity of glycogen synthase kinase 3βwere significantly stronger in cerebral ischemia-reperfusion injury rats subjected to amyloid β-peptide administration than those undergoing cerebral ischemia-reperfusion or amyloidβ-peptide administration alone.Conversely,the activity of protein phosphatase 2A was remarkably reduced in rats with cerebral ischemia-reperfusion injury following amyloidβ-peptide administration.These findings suggest that amyloidβ-peptide can potentiate tau phosphorylation induced by cerebral ischemia-reperfusion and thereby aggravate cognitive impairment.     

Cerebral amyloid angiopathy as a cause of subarachnoid hemorrhage

Cerebral amyloid angiopathy is a pathologic condition characterized by the deposition of amyloid in the walls of small vessels in the cerebral cortex and meninges. Intracerebral hemorrhage is common in persons with this condition, but pure subarachnoid or subdural hemorrhage is rarely seen. Recently, the existence of two types of amyloid proteins related to cerebral amyloid angiopathy, beta protein and cystatin C, has been reported, and immunohistochemical methods using antisera to these proteins have become available. We describe a patient with fatal subarachnoid hemorrhage presumably caused by beta protein-type cerebral amyloid angiopathy, which was demonstrated immunohistochemically by using a monoclonal antibody to a synthetic peptide corresponding to residues 8-17 of beta protein. We suggest that beta protein-type cerebral amyloid angiopathy is a possible etiologic factor in subarachnoid hemorrhage of unknown cause.     

Amyloid angiopathy in a volga german family with Alzheimer's disease and a presenilin-2 mutation (N141I)

We report the neuropathological features in 6 members of a Volga German family with autosomal dominant Alzheimer's disease linked to chromosome 1 who had a presenilin-2 mutation (N¹⁴¹I). The most significant feature in this family was the presence of severe or moderately severe amyloid angiopathy in five family members with clinical dementia. The index case with the presenilin-2 mutation had late-onset dementia at age 73 years, died of an acute intracerebral hemorrhage, and pathologically showed severe amyloid angiopathy but only rare neuritic senile plaques and neurofibrillary tangles. That she was apolipoprotein E ?2/3 heterozygous suggests that the ?2 allele may have exerted a selective protective effect resulting in late onset relatively mild Alzheimer's disease despite severe amyloid angiopathy. This family emphasizes the need for more investigation into the role of presenilin mutation in amyloid deposition, especially in the cerebral vasculature, and the role of these changes in clinical dementia.     

Cerebral amyloid angiopathy with co-localization of prion protein and beta-amyloid in an 85-year-old patient with sporadic Creutzfeldt–Jakob disease

We report on an 85-year-old woman with hypertensive cerebral arteriolosclerosis who presented with rapidly progressive encephalopathy leading to death within 4 months. Magnetic resonance imaging showed mild cortical atrophy consistent with her age and diffuse leukoaraiosis. Her CSF 14–3–3 protein was positive. Neuropathology showed severe spongiform change and gliosis in the grey matter and immunohistochemistry revealed diffuse prion protein deposition in a predominant synaptic pattern. She had no family history of neurological disorder and genotyping did not show any prion protein gene mutation, in keeping with a diagnosis of sporadic Creutzfeldt–Jakob disease. There was also diffuse amyloid angiopathy involving the cortical and leptomeningeal arterioles of the cerebral hemispheres and cerebellum and the capillaries of the grey matter. The amyloid angiopathy expressed beta-amyloid but also prion protein and double immunostaining confirmed co-localization of both proteins in many vessel walls. Alzheimer’s type pathology was restricted to a few diffuse beta-amyloid plaques in the entorhinal cortex and rare tangles in the hippocampus. Deposition of prion protein in cerebral vessels has been reported in a single case of stop codon 145 mutation of the PRNP gene. Co-localization of beta-amyloid and prion protein in the same amyloid plaque has been described in elderly patients with Creutzfeldt–Jakob or Gerstmann–Sträussler–Scheinker diseases but only exceptionally in cerebral amyloid angiopathy. In this patient, hypertensive cerebrovascular disease may have contributed to the failure to eliminate both proteins from the brain.