Case-Based Learning Module

Cauda Equina & Conus Medullaris Syndromes

Learning Objectives

By the end of this session, learners should be able to:

Recognize the hallmark clinical features of cauda equina syndrome (CES), which mimic peripheral nerve dysfunction due to sacral root involvement.
Appreciate that outcomes in CES are variable and strongly influenced by timeliness of diagnosis and treatment.
Differentiate CES from conus medullaris syndrome (CMS), which may appear similar but has distinct neurological signs and causes.

A 66-year-old man presents urgently with progressive difficulty walking.

Past Medical History: Non-Hodgkin lymphoma, treated one year ago with cyclophosphamide, vincristine, prednisone, and rituximab.
Symptoms (3 weeks):
- Gradual onset numbness in thighs → leg weakness → sharp thigh pains.
- Required cane, now walker; physical therapy unhelpful.
- Bowel and bladder control impaired; perineal sensation reduced.
- Denies constipation or frank urinary retention.
- No significant back pain or trauma.
Social History: Former smoker (45 pack-years, quit 18 months ago), no alcohol, retired grocery clerk.
ROS: Negative for fever, weight loss, systemic symptoms.

Vitals: T 97.5°F, P 82, BP 141/83.
General: Overweight, ambulates slowly with walker. Cognition, cranial nerves, and upper extremities normal.
Motor (lower extremities):
- Hip flexion 4/5 bilaterally; hip extension 5/5.
- Knee extension/flexion 4/5.
- Ankle dorsiflexion 3/5.
- Plantarflexion 3/5 (R) / 4/5 (L).
Reflexes: Biceps/triceps 2+; quadriceps/gastrocs absent. Plantar responses flexor.
Sensation: Normal in arms, trunk, lower legs. Impaired in inner thigh, perineum, perianal region (saddle anesthesia).
Coordination: Unable to perform heel–knee–shin; finger–nose normal.
Gait: Very slow, bent knees, requires arm support.

Key diagnostic clues in this case:

These findings localize to the sacral nerve roots within the cauda equina.

Although resembling peripheral neuropathy, the bilateral, sharply localized distribution points specifically to sacral root pathology.

CES vs CMS:

Feature	Cauda Equina Syndrome	Conus Medullaris Syndrome
Reflexes	Hyporeflexia (LMN)	Hyperreflexia (UMN)
Bowel/Bladder	Incontinence, leakage	Retention, constipation
Motor	Asymmetric weakness	More symmetric weakness
Sensory	Saddle anesthesia	Saddle anesthesia (more abrupt onset)

Causes:

CES: Spinal stenosis, infiltrative malignancy, infection (epidural abscess), hematoma, trauma, inflammatory conditions.
CMS: Spinal cord infarct, intramedullary tumors (glioblastoma, ependymoma), multiple sclerosis.

Work-up:

Malignancy-related CES: Prognosis poor; commonly metastatic. Multimodal therapy with radiation, chemotherapy, and sometimes surgery. Early neurosurgery & radiation oncology consults essential.
Spinal stenosis CES: Surgical decompression is often beneficial.
- Outcomes depend on severity and duration prior to treatment.
- Delayed diagnosis → worse recovery.

CES would be most suspicious if:
a. Numbness in legs/feet with diminished reflexes
b. Leg numbness + bladder incontinence
c. Saddle numbness + diminished reflexes
d. Difficulty walking + leg numbness
e. All of the above ✅
CES is difficult to treat because:
a. Cause seldom found
b. Underlying conditions (malignancy, infection, stenosis) often resist treatment ✅
c. Often misdiagnosed
d. Treatment unknown
e. Surgical treatments not optimized
Key differences between CES & CMS include:
a. Numbness of legs
b. Weakness of legs
c. Diminished vs increased reflexes ✅
d. Loss of bladder/bowel sensation
e. Incontinence vs retention ✅
f. Both C and E ✅