Brain Flashcards
Define muscular dystrophy
An inherited group of progressive myopathic disorders resulting from defects in a number of genes required for normal muscle function.
3 categories of genes responsible for muscular dystrophy
- X-linked inheritance:
- Autosomal recessive inheritance:
- Autosomal dominant inheritance:
2 Muscular dystrophies with X-linked inheritance
- Duchenne (most common) & Becker muscular dystrophies
* Emery-Dreifuss muscular dystrophy (EMD Gene)
4 muscular dystrophies with Autosomal recessive inheritance
- Limb-girdle muscular dystrophies 2A, 2B, 2C etc
- Congenital muscular dystrophies
- Emery-Dreifuss muscular dystrophy (LMNA gene)
- Distal dystrophies
6 muscular dystrophies with autosomal dominant inheritance
- Facioscapulohumeral muscular dystrophy
- Limb-girdle musculae dystrophies 1A, 1B, 1C etc
- Myotonic dystrophy Type 1 (DM 1)
- Myotonic dystrophy Type 2 (DM2)
- Distal Dystrophies
- Emery-Drefuss muscular dystrophy (LMNA gene)
Most common form of muscular dystrophy
Duchenne Muscular Dystrophy
Duchenne Muscular Dystrophy: Cause
Caused by a defective gene located on the X Chromosome that is responsible for the production of dystrophin
Dystrophin: Location
Located on the cytoplasmic face of the plasma membrane of muscle fibers
Dystrophin: function
- Functions as a component of a large, tightly associated glycoprotein complex
- Normally provides mechanical reinforcement of the sarcolemma and stabilizes the glycoprotein complex, thereby shielding it from degradation
What happens when Dystrophin is absent?
• In its absence, the glycoprotein complex is digested by proteases → This loss may initiate the degeneration of muscle fibers → Muscle weakness
Clinical course of Duchenne Muscular Dystrophy
- Usually asymptomatic at birth
- Signs of muscle weakness become evident by 2-3 y/o
- Postural muscles of the hip and shoulders are usually first affected
- Pseudohypertrophy (seeming enlargement due to fat tissue) of the calf muscles eventually develops
Duchenne Muscular Dystrophy: Clinical manifestations (7)
- Imbalances between agonist and antagonist muscles lead to abnormal postures and development of contractures / joint immobility
- Scoliosis is common – lateral spinal deformity
- Wheelchair usually needed by 7-12 years
- Smooth muscle of bladder and bowel preserved
- Respiratory muscles often involved: Results in weak and ineffective cough, frequent resp infections, and decreased respiratory reserve.
- Cardiomyopathy is common
- Mortality: Early adulthoo due to resp or cardiac complications
Postural changes in muscular dystrophy (9)
- Shoulders and arms are held back awkwardly when walking
- Sway back
- Belly sticks out due to weak belly muscles
- Weak butt muscles (hip straighteners)
- Knees may bend back to take weight
- Thin, wek legs (especially front part)
- Thick lower leg muscles (‘muscle’ is mostly comprised of fat – not strong)
- Tight heel cord (contractures), child may walk on toes
- Weak muscles in front of leg cause “foot drop” and tip toe contractures
Three types of head injury
- Skull factures
- Parenchymal injury (TBI)
- Traumatic vascular injury
Two categories of Primary Brain Injury and examples
FOCAL INJURY Contusions, lacerations
DIFFUSE BRAIN INJURY: Concussions
What causes diffuse injury?
Shearing
What is often the cause of death with Shaken Baby Syndrome?
Intercerebral Hemmorhage
Define Consciousness: Grades 1-4
- Grade I and II: Some disturbance in attention or memory but no loss of consciousness
- Grade III: May involve brief loss of consciousness (less than 5 minutes)
- Grade IV: Classic Cerebral Concussion: An immediate loss in consciousness that lasts more than 5 minutes but less than 6 hours.
Loss of consciousness involving temporary disruption of ______
Reticular Activating System
Function of Resticular Activating System
Convey all the sensory input coming from the body to be relayed through the cerebral cortex
2 complications of secondary injury
- Seizures
- ICP
Four categories of hematomas
- Epidural hematoma (btwn skull and dura mater)
- Subdural hematoma
- Subarachnoid
Intraparenchymal
Who is most vulnerable to a Subdural Hematoma?
- Young children / babies
- Elderly individuals with any degree of brain atrophy
Types of CVAs: (4)
- Thrombotic Stroke
- Embolic stroke
- Hemorrhagic stroke
- Lacunar stroke
What two types of stroke cause focal ischemia?
Which one causes global cerebral ischemia?
Focal:
- Thrombotic Stroke
- Embolic Stroke
Global:
- Hemorrhagic stroke
Define thrombotic stroke
The development of a clot within an artery of the brain
Risk factors for thrombotic stroke
HTN, Diabetes, smoking
Define Embolic stroke:
Embolus travels to artery (usually from left heart) and causes occlusion
Risk factors for embolic stroke
Heart valve abnormalities
Atrial fibrilation
Common cause of hemorrhagic stroke
- Ruptured cerebral aneurysm
Risk factors for hemorrhagic stroke
- HTN
- Anticoagulants
Define lacunar stroke
o Least common
o Tiny thrombotic strokes that happen in the brain stem – go unnoticed until they become severe
Symptoms of Global Cerebral Ischemia (2)
Non-specific, general symptoms
o Loss of consciousness
o Overall change in mental status
Symptoms of Focal Cerebral Ischemia (4)
Discrete type symptoms related to where stroke is located o Headache o Hemiparalysis o Aphasia o Visual deficits
4 key features of a stroke
(1) Sudden onset
(2) Focal involvement of the CNS
(3) Lack of rapid resolution
(4) Vascular Cause
3 classifications of a stroke based on duration
o “Transient Ischemic Attack” if symptoms last less than 1-2 hours
o “Stroke-in-evolution” (Progressing stroke) cause deficits that continue to worsen as patient is seen
o “Completed stroke” Defined by the presence of persistent deficits (common in embolic stroke)
What is the difference between meningitis and meningeoencephalitis
o Meningitis Def: Infection and inflammation of the meninges
o Meningeoencephalitis Def: Infection and inflammation of the meninges and brain
3 classifications of Meningitis
o Acute Pyogenic: Bacterial Meningitis
o Aseptic: No evidence of pus on spinal tap
o Chronic: Can be viral or bacterial
3 groupings of micro-organisms in Acute Pyogenic Bacterial Meningitis
Microorganisms vary with age:
• Infant: Escheria colia and Group B Strep
• Adolescents and young adults: Neisseria meningitides
• Elderly: Streptococcus pneumoniae and Listeria monocytogenes
What is most commonly the cause of aseptic meningitis
• Enterovirus is the cause in 70% of cases
What is most commonly the cause of Chronic Meningitis
• Usually tuberculosis, syphilis, Lyme’s disease → Diseases that hide in body tissue
Two signs that indicate meningitis
o Kernig’s Sign: Resistance to passive extension of the flexed leg in patient lying supine
o Brudzinski’s sign: Involuntary bending of knees when neck is bent forward (when lying supine)
What is Kernig’s Sign?
Sign of meningitis: Resistance to passive extension of the flexed leg in patient lying supine
What is Brudzinski’s Sign?
Sign of meningitis: Involuntary bending of knees when neck is bent forward (when lying supine)
Ominous signs of impending herniation (death imminent- meningitis)
- Coma
- Papiledema
- Cushing’s triad (bradycardia, respiratory depression, hypertension)
Clinical Manifestations of Meningitis (7)
o Rapid onset of: Fever, headache, lethargy, confusion
o Neck stiffness or nuchal rigidity
o Change in mental status
o 10-30% have cranial nerve dysfunction, focal neurologic signs, or seizures.
o N/V
o Photophobia
o Petechial or purpuric rash, predominantly on extremities, in >half of patients with meningococcemia
Pathophysiology of increased ICP in meningitis
- Metabolic changes: Increased ICP is opposing perfusion pressure, leaving brain vulnerable to ischemia and hypoxia, thus causing more injury and more pressure.
- Body compensates by increasing blood pressure
Three clinical manifestations of increased ICP in meningitis
- Body compensates by increasing blood pressure
- Projectile vomiting
- Headache
Three treatments for increased ICP
o Shunts
o Mannitol: Helps pull fluid out of the cerebral space, uses osmotic pressure
o Hypertonic Saline: Uses osmotic pressure
Two components of consciousness. What does each require?
o 1) Arousal and wakefulness (requires concurrent functioning of RAS and cerebral cortex)
o 2) Content and cognition (Requires a functioning cerebral cortex)
Characteristics of CONFUSION
Impaired ability to think clearly and to perceive, respond to and remember stimuli.
Characteristics of DELIRIUM
Motor restlessness, transient hallucinations, disorientation, sometimes delusions
Characteristics of OBTUNDATION
Decreased alertness with associated psychomotor retardation
Characteristics of STUPOR
Conscious, but with little or no spontaneous activity.
Characteristics of COMA
Unarousable and unresponsive to external stimuli or internal needs.
Often determined by the Glascow Coma Scale.
Glascow Coma Scale
Max Level 15; 5 for each category:
o Eye Opening
o Verbal Response
o Motor Response
Define Brain Death
The irreversible loss of function of the brain, including the brain stem
Clinical manifestations of brain death
• Clinical examination must disclose at least the absence of responsiveness, brain stem reflexes and respiratory effort.
Define Persistant Vegetative State
Characterized by the loss of cognitive functions and unawareness or self and surroundings. Reflex and vegetative functions remain. Bowel and Bladder Incontinence
Minimally conscious state
Level of consciousness ebbs and flows in coma
Locked-insyndrome
The patient has complete cognition, complete wakefulness and awareness but lacks motor ability to demonstrate any of that
Degenerative diseases of the cerebral cortex cause ___________
Dementia Syndromes
Degenerative diseases of the basal ganglia cause ______________
Parkinson’s
Dementia Syndromes (5). Which is the most common?
- Alzheimer’s Disease (AD): Most common Dementia Syndrome
- Vascular Dementia (VaD)
- Parkinson’s Disease with Dimentia (PDD)
- Frontotemporal Dementia (FTD)
- Reversible Dementias: Drug abuse, organ failure can induce this.
What distinguishes Frontotemporal Dimentia (FTD) from Alzheimer’s?
Louis bodies in brains of FTD patients
3 physical findings in alzheimer’s patients
• 1) Brain atrophy
• 2) Beta amyloid plaques: Protein plaques found inside of the axons of nerve cells in the brain (structural protein → constant turnover)
o In alzheimer’s, there is an impairment of that protein turnover.
• 3) Neuro fibrary tangles
o Nerve fibers that clump together and get tangled
o Thought to be an abnormality in the Tau Protein: In microtubules of axon fibers
What are beta amyloid plaques?
How are beta amyloid plaques implicated in alzheimer’s?
Beta Amyloid Plaques are protein plaques found inside of the axons of nerve cells in the brain (structural protein → constant turnover)
o In alzheimer’s, there is an impairment of that protein turnover.
What are neurofibrilary tangles? How are they implicated in Alzheimer’s?
o Nerve fibers that clump together and get tangled
o Thought to be an abnormality in the Tau Protein: In microtubules of axon fibers
Parkinson’s: Definition
o A collection of disorders that all have similar motor manifestations
Parkinson’s: 3 manifestations
- 1) A dampening or slowing down of motor function
- 2) Involuntary tremors
- 3) Muscle spasticity / rigidity
What part of the brain often degrades in Parkinson’s?
Basal ganglia
Role of basal ganglia
“Prunes” brain commands – smooths them out.
What two opposing inputs refine motor command
Dopamine and Acetylcholine
What dopamine component dies off with Parkinson’s?
Substantia Niagra
What is Multiple Sclerosis?
Lesions in brain visible in imaging
Who gets MS?
- More common in women than men
* Onset between 15 and 50
8 Clinical Features of MS
- Parasthesia
- Impaired mobility
- Relapses and remissions
- Optic neuritis
- Lhermitte’s Sign
- Internuclear opthalmoplegia:
- Fatigue
- Uhthoff’s Phenomenon
What is Parasthesia
“Pins and needles” on half of body – mimics sciatica
What is optic neuritis
Extreme bluriness or loss of vision in one or both eyes
What is Lhermitte’s Sign?
: Syndrome where flexion of the neck (forward) causes electric pain down the spine
What is Internucear opthampegia?
Abnormaliity in occulomotor movements – Nystagmus
Uhthoff’s Phenomenon (MS)
Symptoms get worse as body heats
Mechanism of MS
Autoimmune disorder: Patient’s immune system is attacking myelin sheath in brain
Decreased myelenation:
o Slowing down of neuronal firing
o Loss of action potential
Four Clinical Types of MS. Which is the most common?
- Remitting / Relapsing MS (RRMS) ← MOST COMMON
- Secondary progressive MS (SPMS)
- Primary Progressive MS (PPMS)
- Progressive / Relapsing MS (PRMS)
Characteristics of Remitting / Relapsing MS (4)
o Accounts for 85% of MS cases at onset
o Characterized by discrete attacks that generally evolve over days to weeks, often followed by complete recovery.
o Between attacks, patients are neurologically stable.
o Great majority usually evolves into SPMS.
Characteristics of Secondary progressive MS (SPMS) (3)
o Always begins at RRMS
o At some point, becomes a steady deterioration in function unassociated w. acute attacks (may or may not have attacks)
o Produces a greater amount of fixed neurologic disability than RRMS
Characteristics of Primary Progressive MS (PPMS) (2)
o Accounts for ~15% of cases
o Steady functional decline from disease onset
Characteristics of progressive / Relapsing MS (PRMS (4)
o Overlaps PPMS and SPMS
o Acounts for ~5% of MS patients.
o Like PPMS, Patients experience a steady deterioration in their condition from disease onset
o Like SPMS, they experience occasional attacks superimposed on their progressive course.
Dietary treatment for MS
Ketotic Diet
