Parkinson's Disease Flashcards
(90 cards)
Describe the concept of exercise is medicine
- Skilled exercise that entails perceptual & a higher level cognitive processyngtarget prefrontal & associated cortical circuits for executive function
- Aerobic exercise: brood increase in cerebral blood flow including brain circuits in the BG and cerebellum
- Global factors activated: reduced oxidative stress, reduced neuro-inflammation, increased expression of neurotrophic factors
Incidence of Parkinson’s
- 2nd most common neurodegenerative disorder after Alzhiemer’s
- Global data indicate that PD will become a pandemic
Risk factors for PD
- Risk increases with age: prevalence rises sharply after 50 y/o
- White Americans & europeans > black africans
- Family history: autosomal dominant Parkinsonism (synuclein, UCHL1, NURR1, LRRK2) and autosomal recessive disease (DJ1, PINK1, parkin)
- Toxic exposures: carbon monoxide, Manganese, Cyanide, Methanol, MPTP, Neuroleptics, Pesticides/Herbicides
- Infection exposures: Measles, Rubella, Herpes simplex 1 & 2
- Men 1.5x more than women
- More years of formal education increases risk
- Smoking may decrease risk
- High levels of physical exercise may lower one’s risk
Parts of the basal ganglia
- Striatum: caudate nucleus, putamen, & nucleus accumbent
- Lentiform nucleus: putamen & globus pallidus
- Globus pallidus: external and internal segments
- Substantia nigra: pars compacta & pars reticulata
- Subthalamic nucleus (STN)
What is the main input and output region of the basal ganglia (BG)
- Input: striatum
- Output: globus pallidus internal & substantia nigra reticulata
What does the Striatum, Globus pallidus internal, and Substantial nigra reticulata do
- Striatum: receives afferents from the cerebral cortex including motor & premotor, cingulate, & prefrontal cortices, & the intralaminar nuclei of the thalamus
- GPi & SNr: project to the thalamus modulating activity of cortical regions & to the brainstem
Describe goal directed behavior done by the BG
- Caudate head participates in evaluating the full context of potential actions and selects the appropriate action to take
Describe social behavior done by the BG
- Head of the caudate is part of the circuit that recognizes social cues, regulates self-control, and parses out relevant from irrelevant information
Describe emotional/motivation done by the BG
- Ventral striatum (also called the nucleus accumbens) and the ventral putamen involved in seeking rewards, an essential aspect of motivation
- Is involved in predictions when the outcome is unknown
What is the oculomotor function of the BG
- Patients with basal ganglia pathology demonstrate impaired saccadic eye movements
Describe the cortico-BG-thamalic motor circuit
- Hyperdirect pathway: “Stop”; stops ongoing movements
- Direct pathway: “Go”; facilitates desired movement
- Indirect pathway: “No-Go”; suppresses unwanted movements
Describe the Nigrostriatal pathway in the BG
- Composed of dopaminergic neurons whose cell bodies are located in the substantial nigra pars compacta
- Project to the BG and synapse in the striatum
- Parkinson’s: the nigrostriatal pathway degenerates = marked loss of dopaminergic neurons that project to the putamen; more modest loss of those that project to the caudate
Describe normal function of the basal ganglia (BG)
- Target 1: The inhibition of the motor thalamus contributes to a normal level of activity in the corticospinal tracts. This induces these tracts to provide a normal level of facilitation to the lower motor neurons that innervate voluntary muscles.
- Target 2: The IGP inhibits the PPN. Then the PPN inhibits the reticulospinal tracts, which in turn provide the normal level of facilitation to lower motor neurons that innervate postural and girdle muscles, thus controlling muscle tone.
- Target 3: The IGP inhibits the midbrain locomotor region. The midbrain locomotor region stimulates reticulospinal neurons that activate stepping pattern generators, facilitating walking or running.
What does an overactive globus pallidus internus excessively inhibit and result in
- Motor thalamus
- Pedunculopontine nucleus (PPN)
- Midbrain motor region
- Results in: inadequate facilitation of voluntary movement, overactivity of postural & girdle muscles (rigidity), inadequate facilitation of stepping pattern generators for walking
Parkinson’s versus Parkinsonism
- Parkinsonism is a general term that refers to a group of neurological disorders that cause movement problems similar to those seen in Parkinson’s disease such as tremors, slow movement and stiffness.
What disorders fall under Parkinsonism
- Progressive Supranuclear Palsy (PSP)
- Multiple System Atrophy (MSA) aka - - – - Shy-Drager Syndrome
- Vascular Parkinsonism (e.g. basal ganglia strokes)
- Dementia with Lewy Bodies
- Corticobasal Degeneration
- Drug Induced Parkinsonism (anti-psychotics, amphetamines, cocaine)
What is the 1st essential criterion for diagnosing Parkinson’s
- Parkinsonism, which is defined as bradykinesia in combination with at least 1 of either rest tremor or rigidity
Supportive criteria for diagnosis of Parkinson’s disease
1) Clear & dramatic beneficial response to dopaminergic therapy
2) Presence of levodopa-induced dyskinesia
3) Rest tremor of a limb documented in clinical exam
4) The presence of either olfactory loss or cardiac sympathetic denervation on MIBG scintigraphy
Absolute exclusion criteria for Parkinson’s (presence of any one of these features rules out PD)
- Unequivocal cerebellar abnormalities, such as cerebellar gait, limb ataxia, or cerebellar oculomotor abnormalities (eg, sustained gaze evoked nystagmus, macro square wave jerks, hypermetric saccades)
- Downward vertical supranuclear gaze palsy, or selective slowing of downward vertical saccades
- Diagnosis of probable behavioral variant frontotemporal dementia or primary progressive aphasia, defined according to consensus criteria within the first 5 yrs of disease
- Parkinsonian features restricted to the lower limbs for more than 3 yrs
- Treatment with a dopamine receptor blocker or a dopamine-depleting agent in a dose and time-course consistent with drug-induced parkinsonism
- Absence of observable response to high-dose levodopa despite at least moderate severity of disease
- Unequivocal cortical sensory loss (ie, graphesthesia, stereognosis with intact primary sensory modalities), clear limb ideomotor apraxia, or progressive aphasia
- Normal functional neuroimaging of the presynaptic dopaminergic system
- Documentation of an alternative condition known to produce parkinsonism and plausibly connected to the patient’s symptoms, or, the expert evaluating physician, based on the full diagnostic assessment feels that an alternative syndrome is more likely than PD
Red flags/indicators that PD is less likely
- Rapid progression of gait impairment requiring w/c within 5yrs of onset
- Absence of progression of motor symptoms over ≥5yrs
- Early bulbar dysfunction
- Inspiratory respiratory dysfunction
- Severe autonomic failure in first 5yrs of disease
- Recurrent falls bc of impaired balance within 3yrs of onset
- Disproportionate anterocollis (dystonic)
- Absence of any of the common non-motor features of disease despite 5yrs duration
- Pyramidal weakness or clear pathologic hyperreflexia
- Bilateral symmetric Parkinsonism
When is it timely to know a Parkinson’s diagnosis
- Earlier the better: early/asymptomatic: some people will want to know their risk
- Depends on availability of neuroprotective strategies: will only want to know if something can be done to alter risk/asymptommatic disease
- Some will only want to know when symptomatic
- Some may never want to know
Ideas that support early diagnosis of Parkinson’s
- Individual’s right to know
- Highlight opportunities for health improvement & potential disease modification
- Early access to support services
- Opportunity to interact with research
- Provide reason/understanding for symptoms
- Targeted treatment
- Wider window of opportunity to initiate dopamine replacement therapy
Ideas that support against early diagnosis of Parkinson’s
- Individual’s right to not know
- Limited access to specialist services for existing pts
- Impact on insurance/driving restrictions
- Lack of proven disease modifying treatment
- Risk of causing social/psychological harm
- Risk of over medicalization of aging & over diagnosis
- Stigma associated with diagnosis of PD
Subtypes of Parkinson’s Disease
- PIGD (postural instability gait difficulty): late onset PD, faster rate of cognitive decline & a higher incidence of dementia, rapid disease progression more common
- Tremor dominant: young onset PD, good prognosis with slow progression, often initially misdiagnosed as essential tremor
- Mixed Parkinson’s Disease