Pyramidal tracts

pyramidal tracts

1. PYRAMIDAL TRACTS DR MANOJ KUMAR SINGH 1 ST YR PG PHYSICAL MEDICINE AND REHABILITATION

2. PYRAMIDAL TRACTS INCLUDES: 1.Corticospinal tract 2.Corticobulbar tract * These are aggregations of upper motor neuron. *nerve fibres travel from Cerebral cortex and terminate either in brain stem( corticobulbar ) or spinal cord( corticospinal ). *Transmit moter impulses that control motor functions of body.

3. CORTICOBULBAR TRACT Conduct impulses from the brain to the cranial nerves. Fibres from the ventral motor cortex travel with corticospinal tract through the internal capsule. The UMNs synapse directly with the LMNs located in the motor cranial nerve nuclei:- NAMELY- Oculomotor , TROCHLEAR, TRIGEMINAL, ABDUCENS, FACIAL and ACCESSORY and in the nucleus ambiguus to the HYPOGLOSSAL, VAGUS AND ACCESSORY NERVES

4. CORTICOSPINAL TRACT It originate from PYRAMIDAL CELLS in layer V of the cerebral cotex . PRIMARY MOTOR CORTEX SUPPLEMENTARY MOTOR AREA PREMOTOR CORTEX SOMATOSENSORY CORTEX PARIETAL LOBE CINGULATE GYRUS

5. The cells have their bodies in cerebral cotex and AXONS form the bulk of the pyramidal tracts. The nerve axons travel from the cortex through the cerebral peduncle and into the brainstem and anterior medulla. Here they form two prominences called PYRAMIDS OF THE MEDULLA.

6. The axons that cross over move to outer part of the medulla and form the LATERAL CORTICOSPINAL TRACT. Whereas the fibres that remain form the ANTERIOR CORTICOSPINAL TRACT. About 80% of axons cross over and form LCS TRACT. 20% do not cross AND form ACS TRACT.

7. Termination in spinal cord: mostly laminae 3-7, few in ventral horn and laminae 1-2; mostly innervating interneurons , although some innervation of alpha motor neurons Neurotransmitter: glutamate and/or aspartate

8. FUNCTIONS CORTICOBULBAR TRACT- -SWALLOWING -PHONATION -MOVEMENTS OF THE TONGUE -FACIAL EXPRESSION CORTIOSPINAL TRACT- -INVOLVED MOVEMENT OF MUSCLES OF BODY.

9. CLINICAL SEGNIFICANCE Damage to the Corticospinal Tracts The pyramidal tracts are susceptible to damage, because they extend almost the whole length of the central nervous system. As mentioned previously, they particularly vulnerable as they pass through the  internal capsule  – a common site of cerebrovascular accidents (CVA). If there is only a unilateral lesion of the left or right corticospinal tract, symptoms will appear on the contralateral side of the body. The cardinal signs of an upper motor neurone lesion are: Hypertonia  – an increased muscle tone Hyperreflexia  – increased muscle reflexes Clonus –  involuntary, rhythmic muscle contractions Babinski sign  – extension of the hallux in response to blunt stimulation of the sole of the foot Muscle weakness

10. Damage to the Corticobulbar Tracts Due to the  bilateral  nature of the majority of the corticobulbar tracts, a unilateral lesion usually results in mild muscle weakness. However, not all the cranial nerves receive bilateral input, and so there are a few exceptions: Hypoglossal nerve  – a lesion to the upper motor neurones for CN XII will result in spastic paralysis of the contralateral side of the genioglossus . This will result in the deviation of the tongue to the contralateral side. Facial nerve  – a lesion to the upper motor neurones for CN VII will result in spastic paralysis of the muscles in the contralateral lower quadrant of the face.