4. Neurodegenerative
- Definition: disorders characterized by the progressive loss of neurons, typically affecting groups of neurons
with functional relationships even if they are not immediately adjacent.
Note: Most of these diseases are associated with intracellular accumulation of abnormal protein aggregates.
- These diseases can be grouped by clinical presentation into:
- Dementias: e.g. Alzheimer disease
- Hypokinetic movement disorders: e.g. Parkinsonism
- Hyperkinetic movement disorders: e.g. Huntington disease
- Cerebellar ataxias: e.g. Spinocerebellar Degenerations
- Motor neuron disease: e.g. Amyotrophic lateral sclerosis (ALS)
5. Alzheimer Disease
- It is the most common cause of dementia in older adults.
- The fundamental abnormality in Alzheimer disease is the accumulation of two proteins (Aẞ and tau) in
specific brain regions, likely as a result of excessive production and defective removal.
- These proteins lead to neuronal dysfunction and death.
6. Parkinson Disease
- It is a neurodegenerative disease marked by a prominent hypokinetic movement disorder like diminished
facial expression (masked facies), stooped posture, slowing of voluntary movement, festinating gait that is
caused by loss of dopaminergic neurons from the substantia nigra.
- The fundamental abnormality in Parkinsonism is the accumulation of protein aggregates (Lewy bodies)
which are toxic to neurons
7. Demyelinating
- Definition: acquired conditions characterized by preferential damage to myelin with relative preservation of
axons.
-The clinical deficits are due to the effect of myelin loss on the transmission of electrical impulses along axons.
- Examples of demyelinating diseases: Multiple Sclerosis, Neuromyelitis Optica
- Definition: is an autoimmune demyelinating disorder characterized by distinct episodes of neurologic deficits,
separated in time.
Multiple Sclerosis
- Incidence:
- It is the most common of the demyelinating disorders.
- More common in young adult women.
- Pathogenesis:
In genetic predisposed individuals, viral
infection (e.g., EBV) may activate self-
reactive T cells - that react against myelin
antigens and secrete their injurious cytokines.
8. - Morphology:
Gross: MS is a white matter disease. The affected region in brain and spinal cord
appears as firm well circumscribed, somewhat depressed, called plaques.
Microscopically: Active plaque: shows myelin breakdown associated with abundant macrophages and
Lymphocytes
- Clinical Features:
- It often pursues a relapsing-remitting course.
- visual impairment due to involvement of the optic nerve is a frequent Unilateral
initial manifestation of MS
9. Hydrocephalus - Definition: Abnormal dilatation of ventricular system by excess cerebrospinal fluid
with atrophy of the brain tissue.
- Causes:
I. Congenital causes:
(1) Congenital stenosis of the aqueduct cerebri.
(2) Congenital stenosis of the foramina of fourth ventricle.
II. Acquired causes:
(A) Obstruction of CSF flow by: Meningitis fibrous adhesions obstructing the foramina of
the fourth ventricle or the subarachnoid space, Brain tumor or brain abscess.
(B) Deficient absorption of the C.S.F. due to: Obliteration of the subarachnoid space by a
subtentorial space occupying lesion, Thrombosis of the superior sagittal sinus.
10. - Types:
(1) Communicating hydrocephalus: The obstruction is in the subarachnoid space around the mid brain.
(2) Non-communicating hydrocephalus: The obstruction is within the ventricular system or in the roof of the
fourth ventricle.
- Effects:
In infants:
▪️ separation of skull sutures enlargement of the head
▪️ brain atrophy
In Adults:
▪️ increased intracranial tension and may cause brain herniation
11. MCQ
1. Neurodegenerative diseases include the following
except:
a. Alzheimer disease.
b. Parkinsonism.
c. Huntington disease.
d. Amyotrophic lateral sclerosis.
e. Glioblastoma multiforme.
3. Multiple sclerosis is a:
a. Congenital disease
b. Inflammatory disease
c. Degenerative disease
d. Demyelinating disease
e. Metabolic disease
2. Hydrocephalus means abnormal dilation of the
ventricles due to:
a. Severe inflammation
b. Malignant tumors
c. Cerebral aneurysm
d. Accumulation of CSF
e. Cerebral hemorrhage
Put true (T) or false (F)
1- Demyelinating diseases of CNS are
characterized by damage to myelin and axons.
2- Hydrocephalus may be caused by meningitis.
