Basal Ganglia Disordrs

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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