Diseases of the CNS and Neurodegenerative Disorders

Diseases of the CNS

• The nervous system is distinct from other systems as each part of the brain has specialized functions.
• Brain tissue is composed of neurons (nerve cells and fibers) and supporting glial cells (astrocytes, oligodendrocytes, microglial cells).

Neurodegenerative Diseases

• Characterized by progressive loss of neurons, particularly those with intricate functional connections.
• Affect various brain regions, including the hippocampus and cortex (cognitive changes), basal ganglia (movement disorders), and cerebellum (ataxia).
• Alzheimer's disease is a common form, often linked to protein aggregates (Aβ and tau).
• Parkinson's disease is a neurodegenerative disorder resulting from dopaminergic neuron loss in the substantia nigra, leading to symptoms such as tremor, rigidity, bradykinesia, and instability.

Increased Intracranial Pressure

• Defined as CSF pressure exceeding 15 mmHg (200 mm water) in the lateral decubitus position.
• Potential causes include space-occupying lesions, cerebral edema, and obstructive hydrocephalus.
• Common symptoms include projectile vomiting, headache, papilledema, and decreased level of consciousness.

Meningitis

• Inflammation of the leptomeninges (membranes covering the brain and spinal cord) and the subarachnoid space.
• Types include acute pyogenic (bacterial), acute lymphocytic (viral/tuberculosis), and chronic (bacterial/fungal).
• Infection routes can be via the bloodstream (most common) or direct implantation.
• Common causative organisms for acute pyogenic meningitis include E. coli (neonates), H. influenzae (infants and children), N. meningitides (adolescents and young adults), and pneumococcus (very young and old).

Clinical Picture of Meningitis

• General signs of infection, including fever, malaise, and rigor, and petechial eruption.
• Meningeal irritation signs, such as headache, neck stiffness, photophobia, and irritability are common findings.

Complications of Meningitis

• Infection spread to the ventricles, extradural spaces, or thrombophlebitis.
• Possible complications include arthritis, otitis media, endocarditis, and conjunctivitis.
• Healing can lead to fibrosis, obstructive hydrocephalus, compression of cranial nerves, and brain infarcts.

Brain Abscess

• Localized brain tissue suppuration.
• Infection routes include direct implantation (trauma), local extension (e.g., mastoiditis), and hematogenous spread (e.g., from endocarditis).
• Common causative organisms are Staphylococcus aureus, Streptococcus species, and pneumococci, and E. coli.

CNS Trauma

• Includes epidural hematoma, subdural hematoma, and traumatic parenchymal injuries (concussion, diffuse axonal injury, contusion).

Concussion

• Transient loss of consciousness following head trauma.
• Associated symptoms like widespread paralysis, seizures and memory loss about the trauma are common.
• Typically resolves within hours or days with complete recovery, with no lasting anatomical lesion.

Hydrocephalus

• Abnormal dilatation of the ventricular system due to excessive cerebrospinal fluid with brain tissue atrophy.
• Types include communicating and non-communicating hydrocephalus.

Brain Tumors (Primary)

• Benign tumors can be fatal if located in critical positions.
• Usually infiltrative, making complete resection impossible.
• They rarely metastasize but can spread through the cerebrospinal fluid.
• Symptoms arise from local effects and from increasing intracranial pressure.

Tumors of the Nervous System

• Classification includes primary parenchymal, primary non-parenchymal, and metastatic tumors.
• Primary parenchymal tumors originate from neuroglia (e.g., astrocytes, oligodendrocytes, ependymal cells).
• Primary non-parenchymal tumors originate from meninges, nerve sheath cells (e.g., schwannomas, neurofibromas), pituitary gland, or craniopharyngioma, and epidermoid/dermoid cysts.
• Common primary brain tumors include meningiomas.
• Metastatic tumors are the spread of cancer to the brain from other sites (e.g., lung, breast, skin, kidney, gastrointestinal tract).

Meningioma

• Often arises in the front half of the cranial cavity (hemispheric convexity).
• Develops from meningothelial cells of the arachnoid.
• Represents about 20% of primary brain tumors.
• Usually occurs in middle to later life and more common in females.

Explore the intricate world of central nervous system diseases, focusing on neurodegenerative disorders such as Alzheimer's and Parkinson's disease. This quiz covers the anatomical and functional aspects of the brain along with the implications of increased intracranial pressure. Test your knowledge on the specialized functions of brain regions and the effects of neuron loss.