Conus medullaris syndrome

Overview

Conus Medullaris Syndrome is a neurological condition caused by injury to the conus medullaris—the tapered, terminal end of the spinal cord, typically located around the L1 to L2 vertebral level. It results in a mixture of upper and lower motor neuron symptoms, primarily affecting the lower limbs, bladder, bowel, and sexual function. Because of its location, conus medullaris syndrome shares similarities with cauda equina syndrome but has distinct clinical features and requires urgent evaluation and treatment.

Causes

Conus medullaris syndrome is caused by direct injury or compression of the distal spinal cord. Common causes include:

• Spinal trauma: Fractures, dislocations, or penetrating injuries to the lower spine

• Herniated lumbar discs: Especially at L1–L2 or nearby levels

• Spinal tumors: Primary or metastatic tumors compressing the conus region

• Epidural abscesses or hematomas: Causing compression of the terminal spinal cord

• Vascular lesions: Such as spinal cord infarction due to anterior spinal artery compromise

• Congenital malformations: Including tethered cord syndrome or spina bifida occulta (less common)

Symptoms

Symptoms of conus medullaris syndrome often have a sudden onset and involve both sensory and motor functions, particularly in the perianal and perineal region. Typical features include:

• Saddle anesthesia: Loss of sensation in the inner thighs, perineum, and buttocks

• Bladder and bowel dysfunction: Urinary retention or incontinence, fecal incontinence or constipation

• Sexual dysfunction: Impaired erection, ejaculation, or vaginal lubrication

• Lower limb weakness: Mild to moderate, often bilateral

• Hyporeflexia or areflexia: Especially in the ankle and knee reflexes

• Pain: May be less severe than in cauda equina syndrome and localized to the lower back or perineum

Because conus medullaris syndrome affects both upper and lower motor neurons, it can lead to a combination of flaccid and spastic signs.

Diagnosis

Prompt diagnosis is crucial to prevent irreversible damage. The diagnostic workup typically includes:

• Neurological examination: To assess sensory, motor, and reflex changes in the lower extremities and perineum

• MRI of the lumbar spine: Gold standard imaging to visualize compression, trauma, tumors, or disc herniation affecting the conus

• CT scan: Useful if MRI is unavailable or contraindicated

• Bladder ultrasound or post-void residual testing: To detect urinary retention

• Electromyography (EMG) and nerve conduction studies: May be used in chronic cases to assess the extent of nerve damage

Treatment

Treatment of conus medullaris syndrome depends on the underlying cause and the urgency of symptoms. Early intervention is critical. Management options include:

• Surgical decompression: For herniated discs, tumors, abscesses, or hematomas compressing the spinal cord

• Antibiotic therapy: If the cause is infectious (e.g., epidural abscess)

• High-dose corticosteroids: May be used in select cases to reduce inflammation (e.g., in trauma or tumors)

• Pain management: Analgesics or neuropathic pain medications

• Bladder and bowel care: Intermittent catheterization, stool softeners, or bowel regimens

• Physical and occupational therapy: To preserve or improve lower limb strength and function

• Sexual counseling and support: If sexual dysfunction is present

Prognosis

The outcome of conus medullaris syndrome depends largely on the cause, severity, and timing of treatment. Early diagnosis and prompt surgical decompression (if indicated) offer the best chance for neurological recovery. However, persistent bladder, bowel, or sexual dysfunction may occur in some cases. Long-term rehabilitation and support can improve independence and quality of life, though some patients may experience permanent neurological deficits if treatment is delayed.