Cerebral Pathology In Arteriolosclerosis Vascular Dementia

Arteriosclerosis of the small cerebral arteries produces distinct pathologic conditions:

• Subcortical arteriosclerotic encephalopathy

• Lacunar state

• Granular cortical atrophy

• Cribriform state

These conditions may occur alone, but more often they appear in various combinations and manifest with a variety of neurologic symptoms and signs. Most notably, they contribute to the pathology of vascular dementia. Typical neurologic manifestations are parkinsonian features, slow and small step-gait, postural instability, bradykinesia or akinesia, rigidity, pyramidal signs, spas-ticity, pseudobulbar palsy and dysarthric speech, seizures, and urinary incontinence.

The dementia associated with diseases of the small parenchymal arteries is classified as subcortical dementia, to distinguish it from cortical multiinfarct dementia, which is associated with diseases of the large arteries. Small-vessel dementia is characterized by slow psy-chomotility, apathy, poor judgment, lack of insight, moderate memory impairment, and emotional and behavioral changes.

Subcortical arteriosclerotic encephalopathy or Binswanger's disease presents clinically as a slowly progressive subcortical dementia, often complicated by minor strokes. The majority of patients are hypertensive and have several stroke risk factors. Neuroimaging, particularly MRI, is helpful to support the diagnosis, although the changes are not specific. MR images show large periventricular hyperintense lesions (caps and rims), and multiple small and large, often symmetrical lesions in the hemispheric white matter. They are referred to as leukoaraiosis (Greek; white, rarefaction) (Fig. 4.44).

Grossly, the hemispheric and the periventricular white matter is faintly discolored and slightly softened. The histology is characterized by arteriosclerotic changes of the small vessels, multifocal demyelinations in the hemispheric white matter and periventricular zones, and subependymal gliosis (Fig. 4.45).

The vascular changes consist of fibrotic and hyalin thickening of the arteriolar and capillary walls, enlargement of the perivascular spaces, and a dense periadven-titial fibrosis. Some perivascular spaces are filled with plasma fluid.

The myelin changes vary from pale staining and rarefaction, through swelling and varicosities, to breakdown. The extent varies from patchy to diffuse, often extending from the ventricles to the cortex, sparing the subcortical U fibers. Within the demyelinated areas, the density of the nerve fibers is reduced, and the astrocytes are moderately proliferated. Macrophages are sparse. The ependymal lining of the ventricles is disrupted, and subependymal astrocytosis can be prominent. The periventricular veins show collagenosis and luminal stenosis.

FIGURE 4.44

Subcortical arteriosclerotic encephalopathy, Binswanger's disease (BD). A and B. Horizontal T1-weighted MR images show periventricular and multiple small and large confluent hyperintense lesions in the hemispheric white matter. The ventricles are enlarged.

FIGURE 4.44

Subcortical arteriosclerotic encephalopathy, Binswanger's disease (BD). A and B. Horizontal T1-weighted MR images show periventricular and multiple small and large confluent hyperintense lesions in the hemispheric white matter. The ventricles are enlarged.

FIGURE 4.45

Binswanger's disease. A. Fibrohyalinosis and mural thickening of a small blood vessel in the white matter (HE). B. Diffuse and multifocal ischemic demyelination (LFB-CV).

FIGURE 4.45

Binswanger's disease. A. Fibrohyalinosis and mural thickening of a small blood vessel in the white matter (HE). B. Diffuse and multifocal ischemic demyelination (LFB-CV).

The pathomechanism of the disease is not fully elucidated. The demyelination is attributed to chronic ischemia associated with systemic hypotension due to cardiac failure or impaired autoregulation. A suggested alternate mechanism is a late effect of vasogenic edema associated with hypertension.

Lacunar state refers to multiple small cystic cavities that result from the removal of ischemic debris. These lacunae are commonly situated in the subcortical gray structures, brainstem, and hemispheric white matter. Some produce distinct clinical syndromes (Fig. 4.46; Table 4.12).

In granular cortical atrophy, grossly, the cortical surface contains multiple small depressed soft and firm areas. Histologically, these are minute glial scars, small cystic cavities, and laminar cortical necrosis (Fig. 4.47).

Cribriform state refers to multiple miniature cavities, often visible grossly as round, oval, or slit-like smooth-walled cavities averaging 0.5 to 2 mm in size. Typically, they are situated in the basal ganglia and hemispheric white matter. Histologically, the cavities are dilated perivascular spaces that contain one or two thick-walled arterioles or capillaries surrounded by fine fibrous strands or dense collagenous fibers (Fig. 4.48). Corpora amylacea line some cavities. The perivascular myelin may be rarefied, but frank myelin breakdown and macrophage reaction are absent.

Vascular Dementia With Lacunar Infarct

FIGURE 4.46

Lacunar infarct. MRI shows a lacunar infarct in the internal capsule, which manifested with pure hemiparesis in a 58-year-old hypertensive man.

FIGURE 4.46

Lacunar infarct. MRI shows a lacunar infarct in the internal capsule, which manifested with pure hemiparesis in a 58-year-old hypertensive man.

TABLE 4.12.

Common Lacunar Syndromes

Syndrome

Presentation

Localization

Pure motor

Hemiparesis

Posterior limb of

internal capsule

Pontine basis

Pure sensory

Hemisensory

Thalamus

deficit

Ataxic-

Hemiparesis

Posterior limb of

hemiparesis

ipsilateral ataxia

internal capsule

Thalamus

Pontine basis

Dysarthria—

Dysarthria,

Internal capsule

clumsy hand

clumsiness of a

pontine basis

syndrome

hand

Pseudobulbar

Facial diplegia

Bilateral

palsy

Dysarthria

corticobulbar

Dysphagia

tracts

Compulsive

laughing

and crying

FIGURE 4.47

Granular cortical atrophy. A. Gross appearance in the occipital lobe. Cortex from different cases shows (B) small vascular cavity (HE) and (C) subpial and pericapillary glial scars (Holzer stain).

FIGURE 4.47

Granular cortical atrophy. A. Gross appearance in the occipital lobe. Cortex from different cases shows (B) small vascular cavity (HE) and (C) subpial and pericapillary glial scars (Holzer stain).

FIGURE 4.48

Cribriform state. A. Severely dilated, round perivascular spaces in the basal ganglia and slit-like cavities in the subinsular white matter. B and C. The dilated perivascular spaces are filled with fine collagenous fibrillary strands. Occasional hemosiderin pigments are noted (LFB-CV-E).

FIGURE 4.48

Cribriform state. A. Severely dilated, round perivascular spaces in the basal ganglia and slit-like cavities in the subinsular white matter. B and C. The dilated perivascular spaces are filled with fine collagenous fibrillary strands. Occasional hemosiderin pigments are noted (LFB-CV-E).

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