Spastic Paralysis 

- Muscular Weakness on paretic  side with Pronator drift  ( With eyes closed & upper  limbs extended anteriorly & supinated, weak limb will pronate & drift downward )

- Loss of speed and agility on paretic side

- Complete loss of control over distal muscles (Intrinsic muscles of hand)

Abnormal Reflexes

 Increased  DTR’s  ( Hyperreflexia)

Clonus  ( Series of rhythmic alternating contractions of agonist and antagonist muscles ( Lowered threshold for DTR’s)

          -

Clasp-Knife Reflex  (Increased resistance to stretch followed by  loss of resistance - Lowered threshold for DTR’s and Golgi Tendon  Reflexes)

          -

Babinski Sign ( Dorsiflexion of big toe, fanning of little toes after stroking  sole of foot

          -

Hoffmann Sign (Flicking distal phalanx of middle finger results in thumb flexion)

          -

Superficial  Reflexes (Abdominal  [ T8-12 ] & Cremasteric [ L1 ]  are decreased or lost  (Raised thresholds )

SPASTICITY - HYPERTONIA - HYPERREFLEXIA

CAUSES:

   -  Loss of cortical inhibition to Medial Reticulospinal  and Rubrospinal Tracts,

      especially to gamma motor neurons which mediate muscular tone

  -   Loss of Upper Motor Neuron control of Renshaw cells and reflex activity

-   Lateral  Vestibulospinal Tract unabated

Brainstem Centers Controlling Muscular Tone

-Loss of both Cortical control and Cortical inhibition of brainstem centers results in a release of excitation  from brainstem centers on gamma motor  neurons which causes  hypertonia

DECORTICATE

 RIGIDITY

 Syndrome usually produced by bilateral damage to large portions  of cerebral cortex and/or thalamus and characterized by coma and bilateral upper motor neuron spasticity.

Hypertonia seen mainly in  flexors of  upper extremity and extensors of lower extremity. (May be unilateral)

Spasticity and hypertonia produced in large part by loss of  Pyramidal

Tr  and loss of inhibition from premotor cortex to  Brainstem Motor

Centers:  Medial Reticulospinal Tr & Vestibulospinal Tr ( Extensor

Spasticity-Antigravity Posture) and Rubrospinal Tr (Flexor Spasticity

In Upper Extremity).

DECEREBRATE

 RIGIDITY

 Syndrome usually produced by bilateral damage to rostral brainstem(midbrain) and characterized by coma and bilateral upper motor neuron spasticity.

Hypertonia seen in extensors of  neck,  lower extremities,  and proximal extensors of  upper extremities  as well as medial  rotation of upper extremity.

Change in posture from Decorticate to Decerebrate Rigidity

is believed to be due in large part to the loss of the

Rubrospinal Tract which has a strong excitatory input

to proximal flexors of upper extremity. Only  Medial Reticulospinal

Tract and Vestibulospinal Tract remain causing extensor hypertonia.

ALTERNATING  HEMIPLEGIAS

Alternating  Hemiplegias are brainstem lesions which

involve  motor cranial nerves and the Pyramidal Tract.

Alternating motor signs are observed, i.e., Lower

Motor Neuron signs are seen on the Ipsilateral side

and Upper Motor Neuron signs are seen on the

Contralateral side. The most common Alternating

Hemiplegias involve cranial nerves III, VI, and XII.