Neuro pt II Flashcards
Drug Induced parkinsonism
- D2 receptor antagonists (Phenothiazines, treatment of psychosis)
- Drugs that deplete dopamine stores within nerve endings (ie reserpine)
- Metabolite of MPTP (synthetic narcotic), damages nigral SN mitochondria
Vascular parkinsonism
Strokes affecting circuits in basal ganglia - ie, lose regulation
Chronic traumatic encephalopathy
Damage to cerebral blood vessels and other structures ie nigral cells, interactions with midbrain, during violent head movements with excessive cranial acceleration - ie mohammed ali
Encephalitis Lethargica (Viral infection)
Degeneration of SNc
Huntington’s chorea
Genetic hyperkinetic disorder of Basal Ganglia - Loss of spiny neurons at the beginning of the INDIRECT pathway. ie loss of D2R expression. So decreased inhibition to the thalamus, leading to dance like movements.
Other choreas incl sydenham chorea, drug-induced chorea (L-dopa), and athetosis.
hemiballismus
Stroke related hyperkinetic disorder of basal ganglia
Commonly an infarct of STN. Often unilateral, with contralateral manifestation. No longer able to send its positive output to GPi /SNr and thus less inhibition of the thalamus, less inhibition of movement - ballistic movements ie sudden, rapid, flinging, rotational mvmts
Bromocriptine
D2 agonist
Pergolide
D1 and D2 agonist
Amantadine
Increases release of dopamine from surviving Substantia Nigra compacta cells ie treat parkinsons
Selegline (deprenyl)
Blocks breakdown of dopamine (MAOi). Treatment of parkinsons
Entacapone and Tolacpone
Inhibitors of COMT, block bdown of dopamine - parkinsons treatment
Benzotropine
Anticholinergic, muscarinic antagonist. PD treatment, cholinergic projections from substantia nigra to striatal medium of inhibitory path, so decreasing this path.
Surgical therapies for parkinsons
Stereotaxic lesions of subthalamic nuc - reduces excitatory input to GPi - ballismus undesirable prospect
GPi (pallidus internus) lesion - reduces inhibitory input to thalamus directly. Disinhibited thalamus free to restore cortical excitation and reverse hypokinesia
Treatments for huntingtons
Most common is symptomatic - antidepressants
Drugs to limit chorea: antagonists of D2 receptors (activating indirect path), VMAT inhibitors (reduce mvmt of dopamine into vesicles, deminishing exocytosis, reduced dopamine levels, reduced dopamine may dishiibit surviving straitopallidal cells in indirect path)
Alpha Iatrotoxin
Ie black widow. Massive increase of ACh release, tetany.
Lambert-Eaton
Autoimmune antibodies against VG Ca channels
Often in bronchial (oat cell) carcinoma
EPP reduced, not reach stimulus. Reduced reflexes, Muscle weakness - can be improved with activity - ie maintain Ca channel opening
Treat: remove tumour, immunosuppresants, plasma exchang, calcium gluconate can enhance Ca influx, 4-aminopyridine prolongs presynaptic AP
AChEsterase Deficiency
Congenital myasthenia. Accumulation of ACh. EPP amplitude increased and prolonged. Only single mscl nerve stimulation at long intervals produces a single twitch. Repetitive causes EPP temporal summation, –> depolarization block, and reduced muscle twitch
Slow channel syndrome
Congenital myasthenia - ACh binding to nicotinic ACh receptors (nAChR), causes prolonged opening of channels. Prolonged depol, EPP. –> Depolarizatino block, decr muscle twitch.
FOrms of congenital myasthenias
AChEsterase deficiency –> depolarization block
Slow channel syndrome –> prolonged opening, depol block
Fast channel syndrome - close quickly, small EPPs, not reaching threshold
Abnormal binding of ACh to nAChR
Myasthenia Gravis
Antibodies to nAChR. -
Cause cross linking and thus internalization and degradation of nAChR.
Endplat chngs: decreased jnxnl folds, reduced depth, reduced Na channels, less AChR, larger synaptic cleft.
Weakness of voluntary muscles, esp eyes (worked a lot through day, diplopia)
Chronic fatigue, serum from patients can cause disease in animals..
WANING pattern of EMG recordings during rpetitive stimulation
EMG differences MG and LE
In LE (lambert eaton) see a waxing pattern - depolarization is maintained longer, so prolonged opening of Ca channels.
In MG- see a waning pattern, small EPPs not able to invoke AP
Tensilon Test
Injection of edrophonium (AChE inhibitor), muscular strength temporary recovers -diagnostic of myasthenia gravis.
Treatment for Myasthenia gravis
Plasma xchng - temp relef
Immunosuppressants - azathioprine, corticosteroids
Pyridogstigmine (AChE inhibt) in conjuction with propanthline (pyrido is a global AChe ie musc and nic, so propanthaline decreases some side effects).
Thymectomy
Myotonia Congenita
AD - less chloride channelsin muscle membrane. Normally - keep potential close to Ecl during recovery of AP whil K is accumulating in TTS (transverse tubular systm).
Causes increased excitability (closer to threshold) - spontaneous firing after stimulation ceased
–> muscle stiffness and hypertrophy
Decorticate posture
Cerebral lesion (above red nucleus) affecting corticospinal and corticobulbar systms.
Red nucleus –> increases flexion in upper limbs
Pontine and medullary motor centers - promote extension of the legs
Can be elicited by noxious stimuli if not expressed tonically.
Decerebrate posture
Muscle tone of arms favors extension (loss of red nucleus).
Remaining brainstem motor centres contiue promoting leg extension.
Station
Sensitive to damage to conscious and unconscious sensory systems and the motor systems. Ability to stand steadily with feet together - may deteriorate when eyes are closed due to lack of visual compensation.
Intention tremor
Becomes apparent with purposeful movement, and amplitude tends to increase as target is approached. Cerebellar dysfunction is causal
Parkinson’s disease clinical manifestations
Hyposmia - degen of olfac bulbs. Autonomic dysfunction - erectile, cardiac, GI
REM sleep disorder - breakthrough of muscular rigor (pontine degeneration)
Above are all prodromal
Akinesia/bradykinesia, initiation of mvmt difficult
Facial masking - expression diminishes
Rigidity - revealed during assessment of passive mvmt. - Cogwheel rigidity, lead pipe rigidity.
Loss of postural reflexes - patints fall easily if station is disrupted
Shuffling gait, turning difficult, small steps replace pivoting. Festination - unintntional accelration, Gait may normalize with sensory cues
Loss of habituation to glabellar stimulation
Quiet, hoarse, monotonous speech with accelerative bursts (festination)
Stages of Parkinson Disease
- Unilateral
- Bilateral with preserved postural reflexes
- Bilateral with loss of postural reflexes
- Severe disability with some movement
- Akinesia
Athetosis
Writhing movements - tied to BG disease ie athetoid cerebral palsy. Striatal or thalamic injury. Can overlap with choreatic mvmts, or can accompany hemiplegia.
Hungtington’s Presentations
AD, young adults
May first present emotional dysregulation (disinhibition, impulsivity, emotional lability)
Facial/oral musculature - grimacing, eyebrow raising, lingual protrustion
Piano playing postur
Progression - life expectancy two post diagnostic decades
Sydenham’s Chorea
After rheumatic fever, choreatic mvmts emerge (autoimmune) somtimes unilatrally
Aget onset typically 5-15 yrs
Motor manifestations rel to basal gangliar inflammation
Recovery: 6 wks
Deep brain stimulation on parkinson’s
Thalamic stimulation - directly increase excitatory output to cortex
Paradoxical effects of stim of GPi - maybe activation of local inhibitory neurons?
Subthalamic stimulation - mysterious effects
Spino-cerebellum
Overlaps with anterior lobe of cerebellum (above primary fissue). Spinal cord provides this region with sensory feedback regarding consequences of motor activity. Assisting regulation of gross truncal and limb movemtns.
Superior cerebellar peduncles
Cerebellar signals to pons and midbrain (except those destined for vestibular nuclei)
Inferior cerebellar peduncles
Relay information from spinal levels into the cerebellum, also contributes communications with the olive, CN VIII, vestibular nuclei
Middle cerebellar peduncles
Information from pons to cerebellum
Lesion of vestibulocerebellum
Equilibrium disturbances - nystagmus (ocular ataxia), tilted head, titubation (head nodding), truncal ataxia (imbalance) with compensatory wide based stance - impaired tandem wakling
Lesion of spino-cerebellum
Disturbances affect posture and movement of limbs - ataxias of the limbs common (ipsi)
Gait ataxia accompanied by lurching to the side of the lesion
Lesion of cerebro-cerebellum
Affect accuracy and timing of movement. Ataxia (also distal), decomposition of mvmt, dysarthria, dyssynergia (uncoordination of limbs) - dysdiadokinesia (inab to perf rapidly alt mvmts), dysmetria (past-pointing)
Hypotonia, intention tremor, rebound phenomenon
Cerebellar tumour (ie astrocytoma) in midline region
Wide based stance, truncal ataxia, disorder of balance (no heel to toe), nystagmus
Cerebellar stroke (usually one-sided)
IPSI limb ataxia, intention tremor, dysarthria, dysdiachokinesia tc
Thiamine deficiency malnutrtion through alcohol abuse effect on cerebellum
Damages anterior lobe of cerebellum. Dysmetria of legs but not arms. Ataxic stance and gait, intention tremor of legs but not arms
Louis Bar syndrome
(chrom 11) damages cerebellar cortex - massive loss of purkinje cells. Ataxia at first walking, dysarthria, facial and ocular weakness, sensitivity to ionizing radioation, increased vulnerability to cancers, skin and eyes - small dilated blood vessels
Cerebellar Cognitive affective syndrome
Lesions of posterior lobe are considered to correlate with dysfunctional cognitive and emotional systems, lead to emotional blunting and depression, disinhibition and psychosis. Executive, visual-spatial and linguistic deterioration, - dysmetria of thought.
Tropical Spastic Paraparesis (TSP)
(HAM HTLV-1 assoc myelopathy) Degenerative neuro disease - demyelination of the spinal cord. Hyperreflexia, spasticity, weakness of LL and gait abnormality.
Virus, spread via placenta, blood, etc.
Diag. via blood test, MRI, nerve conduction studies EMB
Treat with corticosteroids