13: Nervous System I Pathologies Flashcards
Carpal Tunnel Syndrome
- The median nerve becomes compressed in carpal tunnel syndrome.
- The Carpal Tunnel is a narrow passageway in the anterior wrist that contains tendons and the median nerve.
- This median nerve carries sensory information to the hand and controls movements in the hand and fingers.
Carpal Tunnel Syndrome: Causes
- Fluid retention: pregnancy.
- Overuse –vibrating tools, desk posture.
- Due to: RA, hypothyroidism, acromegaly.
- Trauma (swelling), tumour or fracture in wrist. Small carpal tunnel (congenital).
Carpal Tunnel Syndrome: Signs and Symptoms
- Tingling, numbness orpain in the median nerve distribution.
- Symptoms are often worse at night and can wake patient.
- Weakness of grip and weak thumb opposition.
- Muscle wasting at base of the thumb (sensory symptoms 1st).
Carpal Tunnel Syndrome: Diagnosis
- Tinel’s test & Phalen’s test (+ve if reproduces hand symptoms).
- Nerve conduction studies
Carpal Tunnel Syndrome: Treatment
- Anti-inflammatory drugs, corticosteroid injection, splinting the wrist, physiotherapy.
- Surgery (cutting transverse carpal ligament).
Carpal Tunnel Syndrome: Complications
• In chronic and / or untreated cases, the muscles at the base of the thumb may degenerate.
Bell’s Palsy
The nerve that controls the facial muscles (facial nerve) becomes inflamed or compressed.
Bell’s Palsy: Causes
Viral e.g. Herpes simplex
Surgery
Injury.
Bell’s Palsy: Signs and Symptoms
- Sudden unilateral weakness or paralysis of the facial muscles.
- Cannot close affected eye (can damage cornea).
- Loss of taste & intolerance to loud noise if severe.
Bell’s Palsy: Treatment
Acyclovir
Cortisone
Guillain-Barre Syndrome
- Guillain-Barre is a form of post-infectious de-myelinating disease with ‘neuritis’.
- Associated with acute, ascending, progressive inflammation and demyelination of peripheral nerves.
Guillain-Barre Syndrome: Causes
Auto-immune. 75% are triggered by a recent infection (1-3 weeks after respiratory/GIT infection or post-vaccination e.g. flu / EBV). Antibodies formed against virus cross react with lipids in myelin –molecular mimicry
Guillain-Barre Syndrome: Signs and Symptoms
- Sudden, progressive, bilateral, ascending paralysis.
- Paraesthesia and sensory changes.
- Neuropathic pain into legs.
Guillain-Barre Syndrome: Diagnosis
• Nerve conduction studies, lumbar puncture.
Guillain-Barre Syndrome: Treatment
- Emergency care -respirator, intensive care.
* Plasma exchange, intravenous antibodies, corticosteroids.
Guillain-Barre Syndrome: Complication
Death by heart or respiratory failure.
Multiple Sclerosis (MS)
- An autoimmune inflammatory disease causing demyelination of axons in CNS neurons with damage.
- T lymphocytes attack myelin antigens. Multiple areas of sclerosis (scar tissue) along axons which disrupts conduction.
- Usually occurs between 20-50 years of age, affecting women (2:1) to men.
- Most MS follows a relapsing-remitting pattern(85%). Other patters are progressive.
Multiple Sclerosis (MS): Prognosis
Depends on disease pattern. 15% only suffer one episode. Progressive types have a poor prognosis.
Multiple Sclerosis (MS): Causes
- Vitamin D deficiency –higher prevalence further away from the equator.
* Vitamin D has been shown to ↑oligodendrocyte production of myelin. - Vitamin B12 deficiency –normally acts as a co-factor in myelin formation and also has immunomodulatory effects.
- Genetic susceptibility & environmental trigger, dietary risk factors. Slightly increased risk with family history.
- Viruses e.g. Epstein –Barr Virus (EBV), measles etc.
Multiple Sclerosis (MS): Signs and Symptoms
- Visual symptoms are common: Blindness, loss of vision of one eye & occasional pain (neuritis). Double vision & nystagmus (jerking of eyeball).
- Deafness and loss of balance.
- Burning, pulling sensations.
- Tingling and loss of sensation.
- Bladder urgency and incontinence.
- Cognitive changes and depression.
- Weakness.
Multiple Sclerosis (MS): Diagnosis
• No definite test: based on clinical findings, MRI ophthalmoscopy and CSF analysis.
Multiple Sclerosis (MS): Treatment
Immunomodulatory therapies: Corticosteroids, Interferon-beta,
Physiotherapy
Symptom management
Motor Neuron Disease (MND)
- MND describes the progressive degeneration of motor neurons in the spinal cord, motor cortex & brain stem.
- The current hypotheses focuses on abnormal mitochondrial function causing oxidative stress in motor neurons.
- Sensory functions remain intact.
- Age of onset is typically >40yrs (highest incidence 50-70yrs).
- More commonly affects men.
Motor Neuron Disease (MND): Causes
• Unknown. Suspected link with genetics & environmental toxins and oxidative stress.
Motor Neuron Disease (MND): Signs and Symptoms
- Typically presents as weakness in upper limbs -> dropping objects or difficulty manipulating objects.
- Wasting of hand muscles & tremor of limbs at rest.
- Later stages can affect the legs (tripping), cause slurred speech, dyspnoea, difficulty swallowing.
- Death by respiratory failure -typically within 3-5yrs.
Motor Neuron Disease (MND): Treatment
Currently no cure, specialist care.
Dementia
- Dementia is a syndrome caused by a number of brain disorders, which cause:
- Memory loss.
- Decline in other aspects of cognition.
- Difficulty performing daily activities.
- The prevalence of dementia rises with age.
Dementia: Types
- Alzheimer’s disease (50%) – degeneration of
the cerebral cortex and reduced Acetylcholine
production. - Vascular dementia (25%) - due to
cerebrovascular disease (e.g. due to stroke/s)
and poor oxygen delivery.
Alzheimer’s Disease
• Alzheimer’s is a neurodegenerative disease of the cerebral cortex.
• Associated pathologically with abnormal protein deposition (beta amyloid), atrophy of neurons and less acetylcholine.
• The hippocampus is among the areas first affected, which is important for memories.
The amygdala is often affected later and is a key centre for emotions & memories.
• Whilst progressing, additional regions of brain become affected.
• It is the most common type of dementia (50%)
• 20% of the population affected by 80 years of age.
• Brain deterioration is thought to begin decades before symptoms become evident.
• Global neuron atrophy (& hence brain shrinkage) with disrupted cell communication (Ach).
Alzheimer’s Disease: Causes
• Heavy metal toxicity (degenerate the blood brain
barrier):
•High copper & mercury.
•Aluminium toxicity(e.g. from vaccines, cans, foil etc.).
• Genetic links (account for <1%) – ApoE4 gene.
• Chronic inflammation:
•Such as sugar (& insulin resistance), dairy, gluten.
•Leaky gut (promoting inflammation).
• Pathogens (micro-organisms):
•Oral bacteria such as P.gingivalishave been identified in tissue biopsies.
•Herpes simplex virus.
• Increased risk if cardiovascular disease (CVD) & high homocysteine.
• High levels of oxidative stress.
• Higher cortisol levels (chronic stress).
• Nutritional deficiency e.g. B1, B3, B6, B12, folate, omega-3 fatty acids.
• Hormonal factors:
• Oestrogen deficiency (effects mostly seen in women following full hysterectomy) & Testosterone deficiency.
•Thyroid hormone deficiency.
Alzheimer’s Disease: Signs and Symptoms
Early stages:
• Slight memory loss (especially short term) i.e. forgetting recent conversations.
• Repeated questions & confusion.
• Decreased initiative (↓hobbies, ↓hygiene).
Later stages:
• Significant memory loss (incl. long-term memory).
• Subtle changes in higher order functions i.e. understand jokes.
• Mood disturbances: agitation & aggression.
• “Loss of sense of self” -autobiography (left hippocampus).
• Difficulty with language, unsteady, depression.
Alzheimer’s Disease: Investigations
- Mini Mental State Exam.
* MRI & CT scan.
Alzheimer’s Disease: Treatment
- Drugs: Acetylcholinesterase inhibitors (ineffective).
* Psychological treatments such as cognitive behavioural therapy (CBT).
Alzheimer’s Disease: Pronosis
• People typically live for anywhere between 5 and 20 years after the onset of Alzheimer’s symptoms. The most common cause of death is infection.
Parkinson’s Disease
- A progressive neurological movement disorder affecting movement.
- Caused by loss of dopaminergic neurons in the substantia nigra: an area of the midbrain that regulates movement (and reward).
- Affecting approx. 1% of individuals over 60.
Parkinson’s Disease: Causes
- Mitochondrial dysfunction (oxidative stress).
- Constipation & diet low in polyunsaturated fats. Genetics.
- Toxic environmental factors: i.e. carbon monoxide, manganese poisoning, exposure to pesticides & herbicides.
Parkinson’s Disease: Pathophysiology
2 major neuropathological findings in the medical model:
- Degeneration of dopaminergic neurons in the substantia nigra (midbrain) causing dopamine deficiency leaving patients less able to direct or control their movement.
- Accumulation of abnormal proteins (Lewy Bodies) within neurons.
Substantia nigra
“black substance” –has a darker appearance due to high levels of neuromelaninin dopaminergic neurons.
Parkinson’s Disease: Signs and Symptoms
- Bradykinesia: Short shuffling steps (difficulty stopping/starting).
- Resting tremor(“pill rolling”).
- Stopped/flexed posture.
- Lack of normal subconscious movements (swinging arms).
- Muscle rigidity, mask-like face, low voice.
Parkinson’s Disease: Treatment
- Dopamine replacement (Levodopa/L-dopa).
- Doesn’t cross blood brain barrier very well so high doses needed, side effects can lead to abnormal movements.
- Deep brain stimulation (electrodes in brain).
Huntington’s Disease
- Inherited neurodegenerative disorder affecting the basal ganglia.
- Results in loss of muscle co-ordination (abnormal involuntary jerky movements called ‘chorea’).
- Also causes cognitive impairment and loss of intellect.
- Poor regulation of mood and emotions: psychiatric symptoms (depression, aggression etc.)
- A genetic (autosomal dominant) disease with a defect on chromosome 4.
