Myelopathies.pdf

Myelopathies (spinal cord diseases) The spinal cord is from the C1 to T12-L1 (where the conus medullaris starts). The sensory and ascending (afferent) pathways of the spinal cord are: A. Dorsal column medial lemniscus system (Discriminative touch, vibratory sense, conscious muscle joint sense (propr...

Myelopathies (spinal cord diseases) The spinal cord is from the C1 to T12-L1 (where the conus medullaris starts). The sensory and ascending (afferent) pathways of the spinal cord are: A. Dorsal column medial lemniscus system (Discriminative touch, vibratory sense, conscious muscle joint sense (proprioception)). They decussate in the brainstem. 1. Gracile fasciculus 2. Cuneate fasciculus B. The spinocerebellar tracts 1. Posterior spinocerebellar tract 2. Anterior spinocerebellar tract C. The anterolateral system 1. Lateral spinothalamic tract (pain & temperature) 2. Anterior spinothalamic tract (Light touch & pressure (crude touch)) D. The spino-olivary fibers The motor and descending (efferent) pathways are: A. Pyramidal tracts (rapid voluntary movements at distal ends of the limbs) which decussate at the pyramids. 1. Lateral corticospinal tract 2. Anterior corticospinal tract B. Extrapyramidal tracts 1. Rubrospinal tract (activates flexor muscles and inhibit extensor muscles) 2. Vestibulospinal (activates extensor muscles and inhibit flexor muscles) 3. Reticulospinal tract (inhibit/facilitates voluntary movement) 4. Tectospinal tract (reflex postural movements related to sight) 5. Olivospinal (function is unknown) Symptoms of myelopathy may come from the spinal cord or the structures surrounding it (e.g. vertebra). The posterior root is only sensory while the anterior root is mainly motor (weakness as a symptoms of the lesion) and the autonomic fibers (Sympathetic and parasympathetic). Meningioma is one of the most common tumors affecting the spinal cord (compression) The most important manifestation of myelopathies is the motor dysfunction (may cause myopathies). Myelopathies can be caused by: A. Degenerative discs/spondylosis (most common cause of myelopathy) and dislocations may lead to compressive myelopathy. B. Tumors ----- Extra-medullary (meningioma) or intra-medullary (ependymoma, lipoma) C. Inflammatory/ Autoimmune ----- For example, MS, SLE, Sjorgen, RA D. Infections (rarely) ----- Can be viral myelitis (CMV, VZV, HSV) or poliomyelitis (affecting anterior horn and mostly in children) E. Congenital ----- Syringomyelia F. Vascular (ASA occlusion, Hematomyelia) G. Deficiency ----- Combined sclerosis caused by vitamin B12 deficiency H. Idiopathic/inherited (Spinocerebellar atrophy, spastic tetraplegia) I. Degenerative ----- Motor neuron diseases (Amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) UMN (Pyramidal tract) are from the cortex to the anterior horns. The LMN are from the anterior horns to the Neuromuscular junction. There are a small number of fibers that do not decussate. They will not cause weakness because they are a small number (but may cause spasticity). If the lesion is above the medulla, there will be contralateral weakness in both corticospinal tracts. If the lesion is below the medulla, there will be contralateral weakness in the anterior corticospinal tract and ipsilateral in lateral corticospinal tract (most commonly injured). Types of weakness include: A. Segmental (part of a limb) ---- Mostly seen with LMN lesions (part of the anterior horn). B. Monoplegia ----- Mostly seen in UMN lesions (rarely in LMN) C. Hemiplegia ----- Mostly seen in UMN lesions (rarely in LMN) D. Paraplegia E. Tetra (quadri) plegia Upper motor neuron lesion features include: A. Weakness B. Spastic hypertonia C. Clonus D. Babinski sign UMN Contralateral motor deficits (Upper limbs on extensor and Lower limbs on flexors) Increased tone & spasticity (UL more on flexors and lower limbs more on extensors and adductors) Hyper-reflexia (e.g. DTR) Clonus (Patella clonus and ankle clonus) No atrophy/fasciculations Positive Babinski sign Hoffman sign Abnormal position (flexion in UL and extension in LL) LMN/Radiculopathies Segmental motor deficit (Maximum one limb) Atrophy Hypotonia Decreased or absent DTR Normal skin reflexes in UL (no Hoffman sign) Fasciculations Sensory tract lesions (signs are seen below the lesion) include: A. Spino-thalamic (pain & temperature) B. Posterior column (mainly sensory and) C. Spino-cerebellar (cause ataxia) Cross syndrome occurs under the medulla. There is weakness on the same side of the spinal cord and sensory (pain and temperature) on the other side. If the lesion is in the brainstem, there will be deficiency in one or more cranial nerve on the same side and motor/sensory on the other side. The anterior spinal artery supplies the anterior 2/3rds (in ischemia, the posterior side is spared) Topographic lesions (Cervical, thoracic, lumbar) All of the three topographic lesions will have sensation deficit. Legs, Trunk, Arms Cervical (cervico-brachial plexus) lesions cause ipsilateral hemiplegia (UMN signs). Disc herniation are the most common cause. C4-C5 lesions show full UL and LL motor weakness. C8T1 lesions spare (leave unaffected) the shoulders and the lateral side of the hand. The thoracic lesions will only cause the UMN signs in LL only (ipsilateral monoplegia). The LMN lesions will be segmental (difficult to locate). Sphincters (motor and sensory) may be involved. The Lumbar lesions (anything above L1 will be spared) will cause ipsilateral monoplegia as well. Special syndromes Central cord syndrome ----- The most common form of cervical spinal cord injury. It is characterized by loss of motion and sensation in arms and hands. Can be caused by syrinx or central canal tumor. Brown-Sequard Syndrome ----- Also called hemispinal cord syndrome (lateral compression) Anterior Cord Syndrome ----- Caused by ischemia of the anterior spinal artery, resulting in loss of function of the anterior two-thirds of the spinal cord (sparing the sensation from the dorsal column only) Posterior Cord Syndrome (rarely seen) Conus medullaris and Cauda equina The conus medullaris is at the lower end of the spinal cord. It occurs near L1 and L2. The cauda equina is starts below it from L2 to the sacrum. Amyotrophic lateral sclerosis & Spinal muscular atrophy ALS and SMA are both fatal neuromuscular disease that have no cure. Abdulrahman Algwaiz Sarahah: https://goo.gl/gbxaXx