Is the clinical presentation of conus medullaris syndrome (CMS) typically characterized by bilateral, symmetrical symptoms including lower back pain, sensory and motor deficits, saddle anesthesia, bladder dysfunction, bowel dysfunction, and sexual dysfunction?

Clinical Presentation of Conus Medullaris Syndrome

The clinical presentation of conus medullaris syndrome (CMS) is typically characterized by bilateral, symmetrical symptoms due to its anatomical location and pathophysiology.

Key Clinical Features of CMS

• Lower back pain: Common but non-specific symptom that often presents early in the course of CMS 1

• Bilateral symmetrical sensory deficits: Presents as symmetrical sensory deficits in the lower limbs, reflecting the anatomical organization of the conus medullaris 1, 2

• Bilateral symmetrical motor deficits: CMS classically manifests with a combination of lower motor neuron (LMN) signs at the level of compression and upper motor neuron (UMN) signs below the level of compression 3

  • UMN signs below the level of compression: Symmetric, hyperreflexic paresis of the lower limbs 3
  • LMN signs at the level of compression: Fasciculations and weakness 2, 3

• Saddle anesthesia: Presents as symmetric bilateral perineal numbness, which is a hallmark feature of CMS 1, 2

• Bladder dysfunction: Tends to be more prominent and occurs earlier in CMS compared to cauda equina syndrome (CES) 4, 1

  • Bladder paralysis is common in acute presentations 1
  • May present as urinary retention, urgency, or incontinence 5

• Bowel dysfunction: Associated with early onset of fecal incontinence 4, 5

• Sexual dysfunction: Decreased genital sensation or erectile dysfunction may occur 2, 5

Distinguishing Features from Cauda Equina Syndrome

• CMS presents with a mixed UMN and LMN syndrome, whereas CES is a pure LMN injury 2, 3

• The symmetrical nature of symptoms in CMS contrasts with the often asymmetrical presentation of CES 2

• Bladder dysfunction occurs earlier and is more prominent in CMS compared to CES 1, 5

Diagnostic Considerations

• MRI is the preferred imaging method for diagnosing CMS, providing better visualization of soft tissue, bone marrow, and spinal canal 1

• The conus medullaris is typically located at the L1-L2 disc space by 2 months after birth, and a conus medullaris that ends below the middle third of the L2 vertebra is considered tethered 1

• Neurological examination should focus on:

  • Assessment of perineal sensation 4, 1
  • Evaluation of anal tone 4
  • Testing of lower limb reflexes (may be hyperreflexic below the level of lesion) 3
  • Assessment of bladder and bowel function 1, 5

Clinical Pitfalls and Caveats

• CMS can sometimes present without lower extremity involvement, making diagnosis challenging 6

• The mixed UMN and LMN signs can be confusing and may lead to misdiagnosis 3

• Symptoms may vary depending on the exact level of the conus medullaris injury, with higher injuries showing more predominant UMN signs 3

• Early recognition is crucial as delayed treatment may lead to permanent neurological deficits, including persistent bladder, bowel, and sexual dysfunction 2, 5

• Long-standing untreated cases can result in progressive musculoskeletal deformities, scoliosis, and muscle atrophy 1