basal ganglia disordrs
DESCRIPTION
UG LectureTRANSCRIPT
Basal Ganglia Disorders
Dr Raghuveer Choudhary
Dept. of Physiology
Dr S.N.Medical College
Jodhpur
5/2/2012
BG dysfxnSlow, inefficient actions, rigidity, bradykinesia, unwanted movement
Function Cerebral cortex, basal ganglia, cerebellum and
thalamus– motor activity– muscle tone– organisation of movement
What type ? -cerebral cortex How to perform? -basal ganglia+cerebellum Assist in regulation-thalamus
Function
Part of extra-pyramidal motor system Facilitate behaviour & movement – required and
appropriate Inhibit unwanted & inappropriate
6
Results of Basal Ganglia Impairment
Involuntary Motor Movements Bradykinesia (slow) or Hypokinesia (slow or
diminished) Altered Posture Changes in Muscle Tone
Disease of basal ganglia
– Huntington’s disease – hereditary disease of unwanted movements. It
results from degeneration of the caudate and putamen, and produces continuous dance-like movements of the face and limbs -choreoathetosis
– Hemiballism - Spontaneous,wild & voilent involuntary movements
of one arm and leg (one-sided), which is caused by damage (i.e., stroke) of the subthalamic nucleus.
Parkinson’s Disease
Degenerative (progressive) disorder of CNS
Hypokinetic movement disorder due to decreased motor cortex stimulation by BG (decreased DA release)– Nigrostriatal Pathway (DA-secreting
cells activity) (-) Direct Pathway (+) Indirect Pathway (-) Thalamus
Muhammad Ali in Alanta Olympic
Parkinson’s Disease
Disease of mesostriatal dopaminergic system
PD
normal
PARKINSONISMParkinson's disease is a degenerative disease
of the brain that often impairs motor skills, speech, and other functions.
Parkinson's disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia) and, in extreme cases, a loss of physical movement (akinesia).
Triad of Signs in Parkinson’s
Bradykinesia (esp. movement initiation)
Resting Tremor (Rolling pill)Rigidity
What did you see?
Substantia Nigra, Pars Compacta (SNc)
DOPAminergic Neuron
Slowness of Movement- Difficulty in Initiation and Cessation of Movement
Clinical Feature (1)
Parkinson’s Disease
Clinical Feature (2)
Resting TremorParkinsonian PostureRigidity-Cogwheel Rigidity
Parkinson’s Disease
The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia,
Normally caused by the insufficient formation and
action of dopamine, which is produced in the dopaminergic neurons of the brain.
PD is also called "primary parkinsonism" or "idiopathic PD" (classically meaning having no known cause although many genetic mutations associated with PD have been discovered).
While many forms of parkinsonism are "idiopathic", "secondary" cases may result from toxicity most notably of drugs, head trauma, or other medical disorders.
The disease is named after English physician James Parkinson, who made a detailed description of the disease in his essay: "An Essay on the Shaking Palsy" (1817).
Other causes of parkinsonism- Postencephalitic Severe carbon monoxide poisoining. Toxic agents in well water, agricultural pesticides-
– oxidative metabolities released affect dopamine neurons. Drug induced-
– Antipsychotic: phenothiazines {post synaptic dopamine receptor blocker}.
– Antihypertensive: Reserpine [pre synaptic dopamine receptor blocker].
– Symptoms of parkinsonism accompany- cerebrovascular diseases, Brain tumors, repeated headtrauma.
Motor symptoms- The cardinal symptoms are (mnemonic "TRAP"): Tremor: normally 4–6 cps tremor, maximal when the limb
is at rest, and decreased with voluntary movement. It is typically unilateral at onset. This is the most apparent and well-known symptom, though an estimated 30% of patients have little perceptible tremor; if patient has stroke/ hemeplegia- tremor disappear on that side.
Rigidity: stiffness; increased muscle tone. In combination with a resting tremor, this produces a leadpipe, "cogwheel" rigidity when the limb is passively moved.
Akinesia/ bradykinesia absence of movement and slowness in initiating movements, respectively.
Postural instability: failure of postural reflexes, which leads to impaired balance and falls.
Other signs of Parkinson’s
Postural instabilityShuffling gaitDec arm swingTurning “en bloc”Mask faceMicrographia
Other motor symptoms include:Gait and posture disturbances:
– Shuffling: gait is characterized by short steps, with feet barely leaving the ground, producing an audible shuffling noise. Small obstacles tend to cause the patient to trip.
– Decreased arm-swing, mask face, voice low, monotonus, micrographia.
– Turning "en bloc": rather than the usual twisting of the neck and trunk and pivoting on the toes, PD patients keep their neck and trunk rigid, requiring multiple small steps to accomplish a turn.
– Festination: a combination of stooped posture, imbalance, and short steps. It leads to a Stooped, forward-flexed posture.
– It leads to Gait that gets progressively faster and faster, often ending in a fall.
– In severe forms, the head and upper shoulders may be bent at a right angle relative to the trunk (camptocormia).
Pathophysiology The symptoms of Parkinson's disease result from the loss of
pigmented dopamine-secreting (dopaminergic) cells in the pars compacta region of the substantia nigra These neurons project to the striatum and their loss leads to alterations in the activity of the neural circuits within the basal ganglia that regulate movement, an inhibition of the direct pathway and excitation of the indirect pathway.
The direct pathway facilitates movement and the indirect pathway inhibits movement, thus the loss of these cells leads to a hypokinetic movement disorder. The lack of dopamine results in increased inhibition of the VAN of the thalamus, which sends excitatory projections to the motor cortex, thus leading to hypokinesia.
• Hypokinetic disorders result from overactivity in the indirect pathway. example: Decreased level of dopamine supply in nigrostriatal pathway results in
akinesia, bradykinesia, and rigidity in Parkinson’s disease (PD).
excitation
inhibition
directindirect
D1
D2
D1 & D2 Dopamine receptors
somatosensory cortices
Thalamus
Putamen
GPe
GPi
STN
SNc
motor cortices
GPe/i: Globus pallidus internal/external
STN: Subthalamus Nucleus
SNc: Pars Compacta (part of substantia nigra)
(-)
(-)
(-)(+)
Parkinson’s Disease
Huntington’s Disease
(-)
(-)
Treatment
Parkinson's disease is a chronic disorder that requires broad-based management including patient and family education, physiotherapy, exercise, and nutrition.
At present, there is no cure for PD, but medications or surgery can provide relief from the symptoms.
The most widely used form of treatment is L-dopa in various forms.
L-dopa is transformed into dopamine in the dopaminergic neurons by L-aromatic amino acid decarboxylase (often known by its former name dopa-decarboxylase),
Carbidopa and benserazide are dopa decarboxylase inhibitors.
They help to prevent the metabolism of L-dopa before it reaches the dopaminergic neurons
generally given as combination preparations of carbidopa/levodopa
Huntington’s disease – hereditary disease of unwanted movements. It results from degeneration of the caudate and putamen, and produces continuous dance-like movements of the face and limbs -choreoathetosis
Clinical Feature
Principal Pathologic Lesion: Corpus Striatum (esp. caudate nucleus) and Cerebral Cortex
- Predominantly autosomal dominantly inherited chronic fatal disease (Gene: chromosome 4)- Insidious onset: Usually 40-50- Choreic movements in onset- Frequently associated with emotional disturbances- Ultimately sever dysarthria, progressive dementia ensues.
HUNTINGTON’S CHOREA
SYDENHAM’S CHOREASYDENHAM’S CHOREA
- Fine, disorganized , and random movements of extremities, face and tongue- Accompanied by Muscular Hypotonia- Typical exaggeration of associated movements during voluntary activity- Usually recovers spontaneously in 1 to 4 months
Clinical Feature
Principal Pathologic Lesion: Corpus Striatum
HEMIBALLISMHEMIBALLISM
- Usually results from CVA (Cerebrovascular Accident) involving subthalamic nucleus- sudden onset- Violent, writhing, involuntary movements of wide excursion confined to one half of the body- The movements are continuous and often exhausting but cease during sleep- Sometimes fatal due to exhaustion- Could be controlled by phenothiazines and stereotaxic surgery
Clinical Feature
Lesion: Subthalamic Nucleus
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