Extrapyramidal

Anatomy

• There are two motor neuron system network causing involuntary actions:
  • Pyramidal tracts which directly innervates motor neurons of Spinal cord / Brainstem (Anterior / Ventral) horn cells / Certain cranial nerve nuclei
  • Extrapyramidal system (EPS) which Regulates / Indirect controls of Anterior/ Ventral horn cells.

• EPS is chiefly found in the reticular formation of the pons and medulla.
• EPS originate in brainstem, carrying motor fibers to the spinal cord.
• It is responsible for Unconscious / Reflexive / Responsive control of Reflexes / Muscle tone/ Balance / Posture / Locomotion / Complex movements
• EPS targets lower motor neurons in the spinal cord
• EPS is modulated by Nigrostriatal pathway, Basal ganglia, Cerebellum, Vestibular nuclei and sensory areas of cerebral cortex
• EPS modulate motor activity without directly innervating motor neurons

Function

Name	Explanation	Pathology
Balance	Postural tone adjustment	Ataxia
Reflexes	Preparation of predisposing tonic attitudes for involuntary movements Control of reflexes that accompany the responses to affective and attentive situations (reactions)	Hypo Reflexia
Locomotion	Performing movements that make voluntary movements more natural and correct	Incoordination
Muscle tone	Control of automatic modifications of tone and movements	Rigidity
Complex movements	Control of the originally voluntary movements, then become automatic through Exercise / Learning (e.g., in writing)	Awakwardness
	Inhibition of involuntary movements (Hyperkinesias), which are particularly evident in extrapyramidal diseases.	Tremor

Subdivisions

Functionally, the EPS can be subdivided into four tracts

• Vestibulospinal and Reticulospinal tracts (do not decussate, providing ipsilateral innervation).
• Rubrospinal and Tectospinal tracts (decussate, provide contralateral innervation)

Classification

• Acute dystonic reactions: Painful muscular spasms of neck, jaw, back, extremities, eyes, throat and tongue
  • Oculogyric crisis: An acute dystonic reaction that involves the prolonged involuntary upward deviation of eyes.

• Akathisia: A feeling of internal motor restlessness that presents as tension, nervousness, anxiety and an inability to sit still.
• Parkinsonism: Rigidity + Bradykinesia + Tremor + Tardive dyskinesia
• Pseudoparkinsonism: Rigidity, Bradykinesia, Tremor, Masked faces, Shuffling gait, Stooped posture, Sialorrhoea and Seborrhoea
  • Although Parkinson's disease is primarily a disease of the nigrostriatal pathway and not EPS, loss of dopaminergic neurons in the substantia nigra leads to dysregulation of EPS. Since this system regulates posture and skeletal muscle tone, a result is the characteristic bradykinesia of Parkinson's.
• Tardive dyskinesia: Involuntary muscle movements in the lower face and distal extremities; this can be a chronic condition associated with long-term use of antipsychotics. They are also known as extrapyramidal side effects

Related disease

• Restless Leg Syndrome: Akathisia has very similar sensation
• Parkinson Disease
• RBD

Entities / Miasms

	JE	WNE	CJD	GSS	FFI
Ataxia	+++	+++	+++	+++	+++
Tremor	+++	+++	+	+++	+++
Bradykinesia / Parkinsonism	+++	+++	+++	+++	+++
Rigidity	+++	+++	+++
Choreathetosis	+++
Myoclonus			+++	+++	+++

Note

• It seems that Extrapyramydal sign / Symptoms would be another COE, named EPS COE
• RLS, RBD, Parkinson disease are belonging to this COE

Hypokinesias

• Unlike pyramidal pathology, EPS does not lead to paralysis but instead to Hypokinesia and Akinesia, respectively. Both conditions can express voluntary and involuntary movements.
• Several voluntary acts, such as walking, writing, and speaking, will slow down.
• Bradykinesia: Involuntary movements, a reduction, or loss, of the associated movements of pendulation of the upper limbs during walking or mimic and expressive movements. Furthermore, slowness in the execution of voluntary movements, especially at the beginning of the movement or when this is about to complete, can be present.

Hyperkinesias

• Chorea: sudden, irregular, incomplete, aimless, variable movements
• Athetosis : arrhythmic, slow, exaggerated, tentacular movements
• Hemiballism: the movements are similar to choreic movements but much more intense and persist during sleep
• Stereotypia, Repeated obsessively; they can become voluntarily inhibited, even if with effort
• Tremors: EPS tremor (Typical tremor of PD) is rhythmic, at a slow pace (4 to 5 oscillations per second), not very wide, uniform, more pronounced at rest, and attenuates during voluntary and passive movements - for instance, it disappears during sleep
• Spasms: Involuntary movements of a tonic type (intense and lasting contraction, but transient) or clonic (series of rhythmic contractions of short duration, separated by periods of rest)
• Myoclonus: Rapid, sudden contractions involving isolated muscles or bundles of muscle fibers - usually do not cause motor effects

EPS non-motor presentations

In extrapyramidal diseases, signs and symptoms of a non-motor nature can occur. For example, disturbances of attention, slowed or monotonous ideation, and poor control of emotion and instincts are such findings.

• Spastic crying: it is frequently observable in people with pseudobulbar syndrome, where an insignificant cause can trigger spasmodic or spastic crying
• Forced gaze crisis: oculogyric tonic crisis, with a forced deviation of the eyes, sideways or upwards, lasting from a few minutes to a few hours, which repeats periodically, sometimes accompanied by simultaneous homologous rotation of the head
• Torsion spasm: deformation of the lordotic or kyphoscoliosis back-lumbar spine, with contortion movements
• Spastic stiff neck: rhythmic spasms of rotation and inclination of the body towards one side, sometimes accompanied by a lifting of the corresponding shoulder

Extrapyramidal Syndromes

Pallidal syndrome

This syndrome is characterized by muscle hypertonia, bradykinesia, and sometimes by tremor (hypertonic-hypokinetic syndrome) and is mainly observed in PD. In particular, PD is characterized by generalized extrapyramidal hypertonia, static tremor, and akinesia. The hypertonia is mainly observed at the root of the limbs, is permanent, and is accompanied by an exaggeration of postural reflexes. For example, flexing the hand on the forearm remains for a few moments in this position before reverting. The static tremor predominates in the upper limbs; moreover, it is wide and regular. Akinesia is a loss of the ability to move muscles voluntarily. A typical sign of akinesia is 'freezing.' The patient loses automatic and associated movements, with difficulty regaining balance, and they walk with the center of gravity moved forward or in a stooped posture. Non-motor symptoms such as pain are usually essential features of the disease and can also precede motor disorders.[15][16]

Striated Syndromes

Also termed hyperkinetic-dystonic syndromes include the choreic syndrome characterized by choreic movements and hypotonia; the athetosis syndrome with athetosis movements and hypotonia; the hemiballism syndrome; and the hepatolenticular syndrome, better known as Wilson disease.

Bilateral Injuries At The Brainstem Level

In addition to quadriplegia, two fundamental pictures of hypertonia can be observed, depending on the level of injury: decerebrate rigidity and decorticate rigidity. The EPS plays a key role in both phenomena.

Decorticate Rigidity

Decorticate rigidity occurs when an injury at the superior border of the red nucleus disturbs descending corticospinal and rubrospinal tracts. This condition leads to the flexion of the upper extremities and extension of the lower extremities with painful stimuli.[17] The injury to the red nucleus causes subsequent overactivation of the rubrospinal tract and medullary reticulospinal tract. Also, the lateral corticospinal tract is disturbed, which causes flexor muscles of the lower extremities to be impaired and allows the pontine reticulospinal and medial and lateral vestibulospinal to induce biased extension.

Decerebrate Rigidity

• Decerebrate rigidity occurs when an injury at the superior border of the pons disconnects the posterior aspect of the brainstem and the spinal cord from the rest of the brain. With the transection, stroke, or hemorrhage of the brainstem regions, the lateral ventrospinal tract and the reticulospinal tract over-activate extensor motor neurons with restricted inhibition of the cortex and basal ganglia. This, in turn, causes increased activity of alpha motor neurons and gamma motor neuron discharges.[7] As a result, the injury causes the extensor muscles of all limbs and muscles of the neck and trunk to have increased tone (i.e., the extension of elbows in addition to the extension and internal rotation of all extremities).