Week 5

Extrapyramidal disorders

Presenter : Bayan Al-GhadeerCollege of Medicine – King Faisal University

Learning Objectives

o Basic knowledge• Extrapyramidal system

( structure, function, interconnection)• Role of substantia nigra• Dopamine vs. Acetylcholine

o Movement disorders – Parkinson’s disease• Facts about Parkinson’s disease • Aetiology • Pathophysiology • Clinical features

Introduction

The voluntary movements are controlled by:

• The Pyramidal System• The Extrapyramidal System

The Extrapyramidal System• Main structures

① Corpus striatum

② Subthalamic nuclei

① Substantia nigra

③ thalamus

Basal Ganglia: - Corpus striatum - Amygdaloid nucleus - Claustrum

• Associated structures

④ red nucleus

⑤ reticular formation

⑥ cerebellum

Anatomical organization

• Functions of extrapyramidal system

• selective activation of movements and suppression of others • Initiation of movements

• Setting rate and force of movements

• Coordinating movements

The interconnection between components of the extrapyramidal system and other parts of the brain

Corticostriatel fibers

G

Striatopallidal fibers pallidothalamic fibers

thalamocortical fibers

GABA

P

GABA

P

G

Direct Pathway Indirect Pathway

Corticostriatel fibers

Striatopallidal fibers pallidosubthalamic fibers Subthalamopallidal fibers

pallidothalamic fibers

thalamocortical fibers

G

GABA

P

GABA

P

G

GABA

P

G

excitatory

Inhibitory

How does it really work ?!

G

GABA

PGABA

P

Direct Pathway

excitatory

Inhibitory

Indirect Pathway

G

GABA

P

GABA

P

G

GABA

P

excitatory

Inhibitory

The role of substantia nigra

Consist of two parts:① Pars Compacta: has dopaminergic neurons

serves mainly as input to the basal ganglia circuit, supplying the striatum with dopamine.

② Pars reticulata: has GABAergic neurons serves mainly as output, conveying signals from basal ganglia to other brain structures.

The role of dopamine and acetylcholine

D1

nigrostriatel fibers

nigrostriatel fibers

D

G

D2D

Dopamine excitatory

Inhibitory

D1

nigrostriatel fibers

nigrostriatel fibers

DD2

D

Ach Ach

Ach D

normally

Acetylcholine excitatory

Inhibitory

Movement disorders

Localized neurological diseases Extrapyramidal disease

--> Parkinson’s disease

• Is a neurodegenerative brain disorder • Described by James Parkinson • Annual incidence: 20 per 100,000• Prevalence: 190 per 100,000• Age of onset: 50 years or more• 5% of cases are familial.

Facts about Parkinson’s disease

Aetiology • The cause of the disease is unknown.

Factors play a role

Mutations Environmental triggers 1-methyl-4-phenyl-1 2 3 6-tetrahydropyridine (MPTP)

Pathophysiology

In Parkinson DiseaseNormally

D1

nigrostriatel fibers

nigrostriatel fibers

DD2

D

Ach Achinhibition

GABA

P

GABA

P

excitation

excitatory

Inhibitory

D1

nigrostriatel fibers

nigrostriatel fibers

DD2

D

Ach Achinhibition excitation

GABA

P

GABA

P

G

GABA

P

excitatory

Inhibitory

Clinical features

Motor features

Non-motor features

Motor features

Motor symptoms (Typically asymmetr

ic )

Motor features

Rigidity

> increase muscle tone causing stiffness

> Onset and progression: one arm leg on the same side trunk other body side

> Type of rigidity in Parkinson’s disease # Lead pipe rigidity

# Cogwheel rigidity

Motor features

Rigidity

Cerebral cortex Thalamus

Reticular formation

❶ Reticular formation becomes overactive

❷ Increase muscle tone

❸ Increase resistance to movement

Motor features

Resting tremor

> It’s described as -pill rolling-

> Onset and progression: (develops early in the disease) unilaterally in the upper limb all four limbs

> involuntary rhythmic shaking movement of hands, feet, arms, legs during rest.

> Prominent in the distal portions of the extremities.

Motor features

Bradykinesia

> is slowness of movement and inability or difficulty to initiate or carry out movements despite the presence of adequate strength.

> produces: ① Facial bradykinesia (mask-like face)

② Losing arm swinging while walking

③ Truncal bradykinesia

> dopamine motor cortex activity bradykinesia

Motor features

Postural instability

> difficulty adjusting to postural change leads to poor balance and tendency to fall

Flexed (stooped) posture, more trouble with

walking, may need assistance or need a

wheelchair to get around.

> produces:

Motor features

Others

• Dysphagia (impaired ability to swallow).• Speech disorders.• Gait problems• Fatigue.

Motor features Non-motor features

Autonomic• frequent urination • constipation• impotence• seborrhoea

Cognitive• slowness of thinking• dementia• depression

Other:• Pain - Musculoskeletal pain - Pain associated with dystonia - pain result from tremor

• Sleeping disorders – REM sleep behavior disorders

Summary

o Pyramidal and the extrapyramidal systems both are functioningtogether to control the voluntary movements

o Extrapyramidal system consist of two pathways: direct ( excitatory) pathway and indirect (inhibitory) pathway.

o Parkinson’s disease is a neurodegenerative brain disorder that is characterized mainly by bradykinesia, rigidity and tremor

References • Neurology and Neurosurgery Illustrated, 5E (2010) • Clinical Neuroanatomy, Richard S. Snell, 7E • Fundamental of neurology • http://pathology.mc.duke.edu/neuropath/nawr/motor-systems.html• http://pegasus.cc.ucf.edu/~cwatts/spa3101/Neuro4.html• http://www.mayoclinic.org/diseases-conditions/parkinsons-disease/basics/causes/con-20028488• http://www.uptodate.com/contents/etiology-and-pathogenesis-of-parkinson-disease?source=outline_link&view=text&anchor=H2#H2

Thank you !

Any Questions ?