Week 5: Numb

Week 5: Numb

1. Anatomy of the Spinal cord

   • Spinal nerves
     • Dermatome
       • a strip of skin supplied by a spinal nerve
       • Key Dermatomes in Lesion Localization
     • Myotome
       • a collection of muscles supplied by a spinal nerve
   • Surface Anatomy and Spinal Cord Segments
     • Cervical cord segments: Add ONE to vertebral level
       • Upper thoracic cord segments (T1-T6): Add TWO vertebrae to vertebral level
         • Lower thoracic cord segments (T7-T12): Add THREE vertebrae to vertebral level
           • Lumbar cord segments: Add FOUR vertebrae to vertebral level
             • Sacral and coccygeal cord segments: Add FIVE vertebrae to vertebral level
   • External Features of the Spinal Cord
     • Spinal cord is shorter than vertebral column, ends as "conus medularis" (A) at vertebral level L2
     • Mass of nerves below vertebral level L2 are called "cauda equina" (C)
     • Pia mater covers the spinal cord, ends at L2, while Arachnoid and dura mater extends to S2 (dura sac)
       • CSF in the expanded subarachnoid space between L2 and S2 is the spinal/lumbar cistern
         • Lumbar puncture
     • Pial extension from conus medullaris forms the "filum terminale" (B)
   • Arterial supply
     • Anterior spinal artery - branch of vertebral arteries
     • Posterior spinal arteries - branches of posterior Inferior cerebellar arteries (PICA)
     • Segmental spinal arteries
       • Artery of Adamkiewicz: supplies the lower thoracic or upper lumbar region
   • Venous drainage
     • Spinal veins drain to the internal vertebral plexus in the extradural space
     • Also communicates with intracranial veins and pelvic venous plexuses
     • No valves
   • Spinal cord segments

2. Physiology

   • Sensation
     • the process of sensing our environment through touch, taste, sight, sound, and smell.
     • Characteristics
       • Modality
       • Intensity
       • Location
       • Duration
     • Fibers
     • Receptors
   • Ascending tracts
     • Dorsal Column-Medial Lemniscal
       • Origin: Dorsal Horn (Nucleus Cuneatus/Gracillis)
         • Cross Over: Decussation of MO
           • Relay : Thalamus
             • Destination : Somatosensory Cortex
               • First order (From skin) Second order (to thalamus) Third order (to SSC)
                 • A Beta fibers
                   • touch (tactile sensation), vibration and proprioception
     • Spinothalamic
       • Origin : Dorsal Horn of SC
         • Cross Over: Spinal Cord
           • Relay : Thalamus
             • Destination : Somatosensory Cortex
               • First order (From skin) Second order (to thalamus) Third order (to SSC)
                 • Adelta and C fibers
                   • Neurotransmitter Substance P
                     • Anterior spinothalamic tract – carries the sensory modalities of crude touch and pressure. Lateral spinothalamic tract – carries the sensory modalities of pain and temperature.
     • Spinocerebellar
       • Origin:
       • Cross Over : DON’T (except anterior)
         • Destination: Cerebellum
           • First order (From muscle) Second order (to cerebellum)
             • A Alpha fibers
               • unconscious proprioceptive information
   • Descending tracts
     • Pyramidal tracts
       • Corticospinal tracts – supplies the musculature of the body
       • Corticobulbar tracts – supplies the musculature of the head and neck.
       • the voluntary control of the musculature of the body and face
     • Extrapyramidal tracts
       • involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion

3. Biochemistry

   • Hyperglycemia induced tissue damage
     • Capillary endothelial cells (retina)
     • Mesangial cells (renal glomerulus)
     • Neurons & Schwann cells (peripheral nerves)
     • Overactivity of Polyol pathway
     • Advanced Glycation End (AGE) products pathway
     • Activation of Protein Kinase C pathway
     • Overactivity of hexosamine pathway

4. Pathology of Peripheral Neuropathies

   • Axonal Neuropathies
   • Demyelinating Neuropathies
   • Anatomical Classification
   • Inflammatory Neuropathies
     • Acute
       • Guillain-Barré Syndrome
     • Chronic
       • Chronic Inflammatory Demyelinating Polyneuropathy
   • Metabolic, Hormonal & Nutritional Neuropathies
     • Diabetic Neuropathy
     • Uremic Neuropathy
   • Toxic Neuropathy
   • Inherited Neuropathy
     • PMP22 neuropathies

5. Pharmacology

   • Treatment goals
     • Glycemic control
       • Preventing extensive foot tissue damage
         • Pain management
           • Morphine Tramadol Lidocaine
   • Anti-Depressants
     • TCAs
       • Amitriptyline Doxepin Imipramine Clomipramine
   • Anti-Convulsants
     • Gabapentin
       • Alpha2-delta1 subunit ligand of calcium channels
       • Presynaptic inhibitor of the release of excitatory neurotransmitters including glutamate, substance P, and calcitonin gene-related peptide (CGRP)
       • Sedation , Ataxia
   • Mood stabilizer
     • Sodium Valproate
       • Sodium channel blockade, blockade of GABA transaminase (enzyme that metabolizes GABA), and T-type calcium channels blockade
       • GI distress hepatotoxicity Pancreatitis

6. Epidemiology

   • prevalence of diabetes in Qatar is 12.5% and is estimated to increase to 14.3% by 2030
     • the prevalence of neuropathy was 9.5%

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