Motor Pathways Dr Ayman G. Abu-Tabanja

Upper Motor neurons: Supra spinal neurons whose axons descend in bundles (descending tracts) that innervate lower motor neurons Lower motor neurons: Motor neurons whose cell bodies are situated in the anterior horn of the spinal cord or motor nuclei of cranial nerves and whose axons innervate skeletal muscles

Motor Pathways

Lateral Corticospinal Tract Direct motor pathway Contralateral innervation of LMN LMN Innervates the trunk and Upper and Lower limbs Voluntary, discrete & skilled movements

Posterior limb of internal capsule Cerebral peduncle in midbrain Basal part of Pons Pyramid in medulla Motor Decussation in rostral medulla Lateral Funiculus

Corticobulbar Tract Direct Motor Pathway UMN innervate LMN bilaterally Exception: Facial motor nucleus which supply the muscles of the lower part of the Face Hypoglossal motor nucleus which supply genioglosus

Somatotopic Representation of Corticospinal & Corticobulbar Fibers

Upper & Lower Motor Neurons Lesions Upper motor neurons lesion: Location Signs: Paralysis or paresis Hypertonia Abnormal reflexes Exaggerated reflexes Muscle atrophy is not common

Plantar flexion Versus Dorsal flexion

Upper & Lower Motor Neurons Lesions Location Signs: Paralysis Hypotonia Loss of reflexes Muscular fasciculations Muscle atrophy Muscle contracture

Upper & Lower Motor Neurons Lesions of the face Upper motor neurons lesion Signs: Paralysis of Contralateral lower quadrant of face Lower motor neurons lesion: Location: motor nucleus of facial nerve Paralysis of Ipsilateral half of face

Reticulospinal tract Originate from reticular formation In brainstem Facilitate or inhibit voluntary muscle activity

Tectospinal Tracts Originate from superior colliculus Upper cervical segments Cross medline (most fibers) Reflex postural movements of the head in response to visual stimuli

Rubrospinal Tract Originate from red nucleus Cross medline immediately Facilitate Flexors Inhibit Extensors

Vestibulotospinal Tracts Originate from vestibular nuclei Facilitate Extensors Inhibits Flexors Maintenance of balance

Lesions to extrapyramidal tract Severe Paralysis Spasticity Exaggerated deep muscle reflexes Clasp knife reaction