Medicine Marrow Pg No 657-666 (Neurology)

Ventral/Anterior Tracts

• Ascending tracts carry sensations of pressure and crude touch
• Descending tracts include Extrapyramidal and Corticospinal tracts
• Extrapyramidal tracts involve the Vestibulospinal, Ventral reticulospinal, and Tectospinal tracts
• Corticospinal tracts control extension

Pathology of Descending Tracts

• Early stage: Paraplegia in extension due to corticospinal tract involvement
• Late stage: Paraplegia in flexion due to progression of disease and involvement of extrapyramidal tracts

Brown Sequard Syndrome

• Hemisection of the spinal cord can result in:
  • Ipsilateral loss of posterior column sensation and motor weakness
  • Contralateral loss of lateral spinothalamic sensation (pain and temperature)

Blood Supply of Spinal Cord

• Arteries:
  • Superior cerebellar artery, Middle cerebellar artery, Posterior inferior cerebellar artery, Posterior cerebral artery
  • Basilar artery, Vertebral arteries
  • Ascending cervical, Intercostal, Lumbar arteries
  • Anterior spinal artery, Posterior spinal artery, Dorsal radicular artery, Ventral radicular artery

Cross-section of Spinal Cord

• Sensory and motor pathways:
  • Fasciculus cuneatus
  • Fasciculus gracilis
  • Dorsal root
  • Dorsal spinocerebellar tract
  • Ventral spinocerebellar tract
  • Lateral spinothalamic tract
  • Ventral spinothalamic tract
  • Anterior horn
  • Lateral corticospinal tract (pyramidal tract)
  • Rubrospinal tract
  • Lateral reticulospinal tract
  • Vestibulospinal tract
  • Ventral reticulospinal tract
  • Tectospinal tract

Root pain/girdle pain vs Lhermitte sign

• Root pain/girdle pain:
  • Brief shock-like pain along a distribution, initially unilateral, then bilateral
  • Exacerbated by coughing/Valsalva maneuver
• Lhermitte sign:
  • Shooting pain along the spinal cord, extending to the sacrum
  • Exacerbated by flexion of the neck

Useful for Localization

• Funicular pain/tract pain: Constant, dull aching pain from within
• Suspended sensory loss: Loss or crossing over of sensory tract fibers above and below the level of the spinal cord involvement; sensation below the level is considered normal
• Dissociative sensory loss: Loss of spinothalamic tract sensation with intact posterior column
• Early LMN findings (Lower Motor Neuron): When lesions reach the anterior horn cells
• Spinothalamic tract fibers: These fibers are organized centrally to peripherally (e.g., cervical, thoracic, lumbar, sacral) and therefore, sacral sparing may be present when involvement is intramedullary. Bowel and bladder fibers are also centrally located, indicating early involvement. Corticospinal tracts are peripherally located, implying late involvement.

Other observations

• CSF protein: Increased protein levels might suggest root involvement
• Intramedullary: Extension of the pathology can damage sympathetic fibers in the cervical level, causing Horner's syndrome

Acute Transverse Myelitis

• Rapid onset full thickness/segmented monophasic inflammation of the spinal cord (myelitis: Inflammation of cord)
• Demyelinating disease which can affect variable number of segments
• Causes:
  • Post infectious (most common)
  • Vaccination
  • Multiple sclerosis
  • Sarcoidosis
  • Paraneoplastic
  • Neuromyelitis optica
  • Behçet's disease

Levels of Principal Dermatomes

• C5: Clavicles
• C5,6,7: Lateral parts of upper limbs
• C8, T1: Medial sides of upper limbs
• C6: Thumb
• C6,7,8: Hand
• C8: Ring and little fingers
• C8, T4: Level of nipples
• T10: Level of umbilicus
• T12: Inguinal or groin regions
• L1,2,3,4: Anterior and inner surfaces of lower limbs
• L4,5, S1: Foot
• L4: Medial side of great toe
• S1, 2, L5: Posterior and outer surfaces of lower limbs
• S1: Lateral margin of foot and little toe
• S2,3,4: Perineum

Clinical Features

• Paresthesia: Beginning in the feet and extending upward to trunk
• Back pain and paraesthesia: Evolve into spastic weakness
• Peak reached: Within 4 hours to 21 days
• Plateau phase: Mean duration 1 week
• Definite sensory level:
  • Band-like constriction at the level
  • Complete loss of all sensory modalities below the level
  • If half thickness involvement: U/L posterior column loss + C/L spinothalamic loss
• Motor weakness: Below the level of involvement (Paraparesis: Symmetrical/asymmetrical)
• Significant bowel/bladder involvement: Urinary retention
• Brisk reflexes: Below the level of involvement

Descending Tracts

• Lateral Corticospinal Tract:
  • Location: Pre-central gyrus
  • Pathology:
    • Extramedullary lesion: Early involvement
    • Hemisection of spinal cord: 1/L motor weakness
• Rubrospinal Tract:
  • Only extrapyramidal pathway in lateral column
  • Action: Flexion of upper limb
  • Pathology:
    • Lesion w.r.t Red nucleus of mid Brain
    • Decorticate rigidity: Upper limb is flexed; Lower limb is stretched
    • Decerebrate rigidity: Upper limb is stretched; Lower limb is stretched

Spinal Cord Tracts

• Spino-cerebellar
• Spinotectal
• Spinoreticular
• Spino-olivary

Effects of Lesions on Spinal Cord Tracts

Conus Medullaris v/s Cauda Equina

Epiconus

• Involves: L4, L5, S1, S2
• Lower limb weakness: Hip flexion/adduction spared
• Knee & ankle jerk lost
• Sensory loss: Lower limb (Thigh spared)
• Bladder: UMN

Non Compressive Myelopathy

• Causes:
  • Vascular & demyelinating:
    • Vascular: Anterior spinal artery (ASA) thrombosis
    • Demyelinating: Multiple sclerosis (ms), Neuromyelitis optica (NMO)
  • Inherited: Friedreich's ataxia
  • Toxin: Arsenic
  • Autoimmune: Sarcoid
  • Metabolic:
    • Sub acute combined degeneration: Posterolateral cord syndrome, D/t vitamin B12 deficiency
      • Differential diagnosis: Vitamin E deficiency, Copper deficiency
  • Other factors: HIV, HTLV-I

Anatomy of Spinal Cord

• Origin: Vertebral Artery
• Branches:
  • 2 posterior spinal arteries: Posterior 1/3rd of spinal cord
  • 1 Anterior spinal artery: Anterior 2/3rd of spinal cord
  • Radicular arteries (Feeder arteries):
    • Reinforce blood supply at each level (Lower cervical segment and below)
    • Artery of Adamkiewicz/Arteria radicularis magna (Largest radicular artery):
      • Originates near T8-T12 vertebrae → Supplies entire lower half spinal cord
    • T4-T5 Spinal Segments: Less radicular arteries → Increased risk of ischemia
    • Arteria Vasocorona: Circumferential anastomotic channels around spinal cord.(Corticospinal tract in watershed area → myelopathy).

Pathology

• Anterior Spinal artery thrombosis:
  • Onset: Acute
  • Associated with: Generalized atherosclerosis
  • Sparing of posterior column
• Posterior spinal artery injury: Traumatic accidents

Ligamentum denticulatum

• Extension of pia mater attaching spinal cord on duramater
• Compressive myelopathy: Denticulate ligament compresses corticospinal tract

### Compressive Myelopathy

• Chronic course
• Types & causes:
  • Intramedullary:
    • Cause:
      • Tumors: Ependymoma, Oligodendroglioma, Medulloblastoma
      • Expansion of cavity: Syringomyelia
  • Extramedullary:
    • Intradural:
      • Cause: Neurofibroma, Meningioma
    • Extradural (most common):
      • Cause:
        • Lesion of vertebrae: Fracture, Infection (TB, syphilis), Pyogenic abscess
        • Metastasis (Prostate & ovary cancer)
        • Disc pathology: IVDP (most common)
        • Aneurysm of aorta

Clinical Features

• Chronic back pain: Moderate to severe intensity, worse in upright posture (neurogenic claudication; canal diameter decreases in standing/erect posture). Relief from bending (like cycling)
• Tingling, numbness, paresthesia: Typically on both lower limbs, depending on the affected spinal level
• Weakness in lower limbs
• Band-like sensation (hyperesthesia): At the level of involvement (e.g., umbilicus if T10 level is involved)

Neurogenic Claudication vs Vascular Claudication

Examination Findings

• Higher mental function (HMF), cranial nerves (CN): Normal
• Motor:
  • Upper limb: Compression below T1 → power intact (5/5)
  • Lower limb: Reduced power
• Sensory:
  • Upper limb: Compression below T1 → sensation intact
  • Lower limb:
    • Spinothalamic tract loss
    • Posterior column loss
• Reflexes:
  • Lower limb: Exaggerated (knee jerk, ankle jerk)
  • Plantar: Extensor
• Bowel & bladder involvement: Possible in cases of intramedullary compression

Differentiating Points from GBS

• GBS:
  • Progressive lower limb weakness (Proximal > distal)
  • Ascending paralysis
  • Areflexia
  • Normal sensory examination
  • No band-like sensation (definite sensory level)
  • No bladder symptoms

Investigations

• MRI T2 of spine: Hyperintensities at the level
• CSF: Pleocytosis (>10 cells), ↑ IgG index

Treatment

• No response
• High-dose methylprednisolone: (500-1000 mg IV in 100ml NS over 1 hour)
• Indications for plasma exchange:
  • Inability to walk
  • Markedly impaired autonomic function
  • Sensory loss in lower extremities

SUBACUTE COMBINED DEGENERATION (SACD)

• AKA posterolateral cord syndrome (White matter)
• D/t vitamin B12 deficiency

Progression of disease

• Posterior tract: Posterior column sensations lost. Tingling, paresthesia of distal extremity: First symptom
  • Vibration sense lost first: First sign
  • Fine touch and proprioception lost
  • Sensory ataxia, gait abnormality
• Lateral tract:
  • Spinothalamic tract
  • Corticospinal tract: umN findings (Babinski: extensor plantar)
  • Motor manifestations
• Large fibre neuropathy: Reflex lost (Knee jerk, ankle jerk), glove & stocking neuropathy
• If not treated: Complication: Dementia, optic atrophy

Level Localization

• LMN findings: Wasting atrophy, band-like sensation, hyperesthesia, hypesthesia, hypoalgesia. At the level of the lesion
• UMN findings: Below the level of lesion (Superficial reflexes lost, deep reflexes exaggerated)
• Upper limb normal: Lesion below T1 (Above the level of involvement: spared)
• Sensory symptoms: In both lower limbs
• Weakness: Of both lower limbs
• Beevor's sign positive: Lesion below T10
• Once the spinal segment is localized: Localize compression to the corresponding vertebral segment
• Reflex level: Best localizing value

Beevor's Sign

• Procedure: Ask the patient to get up from a supine position
• Principle:
  • Normal: Upper (T7-T9) and lower (T9-T12) abdominal muscles contract together. No deviation of the umbilicus
  • Weakness of lower abdomen: Upper abdominal muscle contraction pulls umbilicus above (Beevor sign positive)

### Extramedullary vs Intramedullary Compression