Complete evidence-based clinical architecture: Interactive Axial Tractography, Conus vs. Cauda Equina, Outside-In vs. Inside-Out Somatotopic Lamination, Pathognomonic Reflexes & Special Tests, Classic Spine MRI Signs (“Owl's Eyes”, “H-Sign”, “Bright Spotty”, “Trident”, “Inverted V”), and 2024 McDonald / 2023 MOGAD / 2015 IPND NMOSD Criteria.
Select any classical spinal cord syndrome below to visualize damaged ascending/descending tracts and clinical localization rules.
Primary Lesion at 1. CERVICAL (C5–C8): interrupts [C, T, L, S] fibers. Descending LCST degenerates caudally; Ascending DC/STT blocks [C, T, L, S] input rostrally.
Ipsilateral motor + dorsal column loss with Contralateral spinothalamic loss 1–2 levels below.
Lateral hemisection of the spinal cord (Left or Right half)
IPSILATERAL UMN weakness (spastic monoparesis or hemiparesis below the lesion) because lateral corticospinal tract already decussated at the caudal medulla (pyramidal decussation).
CONTRALATERAL loss of pain and temperature starting 1–2 segments BELOW the lesion because second-order fibers ascend 1–2 levels in Lissauer tract before crossing in the anterior white commissure.
IPSILATERAL loss of vibration and proprioception below the lesion because fasciculus gracilis & cuneatus ascend uncrossed until the caudal medulla (nucleus gracilis/cuneatus).
IPSILATERAL segmental LMN weakness/areflexia and ipsilateral radicular/band-like allodynia or complete anesthesia AT the level of the lesion; ipsilateral Horner syndrome if cervical/T1.
| Clinical Feature | Conus Medullaris Syndrome (Terminal Cord S2–S5) | Cauda Equina Syndrome (Lumbosacral Roots L2–S5) |
|---|---|---|
| Anatomical Level | Sacral cord segments (S2–S5) located at T12–L2 vertebral bodies | Lumbosacral nerve roots (L2–S5) below L2 vertebral level in lumbar cistern |
| Onset & Symmetry | Sudden / Acute and BILATERAL, SYMMETRIC | Gradual / Subacute and UNILATERAL or ASYMMETRIC |
| Pain Character | Mild or moderate localized low back / perineal ache (radicular pain uncommon) | SEVERE, lancinating asymmetric radicular sciatic pain radiating down legs |
| Sensory Deficit | Symmetric "Saddle Anesthesia" (perianal S3–S5), may show dissociated sensory loss | Asymmetric saddle hypoesthesia + asymmetric L2–S2 dermatomal numbness in legs |
| Motor Weakness | Mild, symmetric distal weakness (often minimal leg weakness); fasciculations possible | Marked, asymmetric flaccid LMN paraparesis (foot drop, knee extension/hip flexion weakness) |
| Deep Tendon Reflexes | Mixed UMN + LMN: Patellar (L4) preserved or brisk; Ankle (S1) absent; Babinski may be POSITIVE | Pure LMN: Both Patellar (L4) and Ankle (S1) reflexes diminished/absent; Plantar flexor (NO Babinski) |
| Sphincter & Sexual Function | EARLY & PROMINENT urinary retention/overflow incontinence, fecal incontinence, erectile dysfunction, absent bulbocavernosus/anal wink reflex | LATE presentation of urinary retention (high post-void residual) and sphincter loss |
| Classic Etiologies | MOGAD (classic conus predilection!), L1 burst fracture, Ependymoma, SDAVF, Schistosomiasis | Massive central L4–L5 or L5–S1 disc herniation, Epidural metastasis/abscess, CMV polyradiculitis, Elsberg syndrome (HSV-2), Myxopapillary ependymoma |