Summary Cauda equina syndrome (CES) is caused by severe compression of nerve roots in the thecal sac of the lumbar spine, most commonly due to an acute lumbar disc herniation Early diagnosis is critical and is made clinically by characteristic symptoms of saddle-like paresthesias combined with acute back and leg pain. The cause is confirmed by urgent MRI Treatment is prompt surgical decompression that should be performed within 24 hours, and absolutely within 48 hours ETIOLOGY Epidemiology incidence rare (annual incidence of 1.5-3.4 cases per million) login to view 2 more bullets occurs with ~3% of all lumbar disc herniations demographics more common in males 4th decade (30s) of life is the most common age group location most commonly occurs at the L4-5 level Pathophysiology pathoanatomy massive space-occupying lesion within lumbosacral canal login to view 14 more bullets pathobiology mechanical compression decreases nutrient delivery to the nerve root login to view 2 more bullets intraneural compartment syndrome login to view 2 more bullets Associated conditions orthopedic conditions conus medullaris syndrome lumbar disc herniation spinal cord tumor spondylolisthesis lumbar burst fracture sacral fracture epidural hematoma medical conditions deep vein thrombosis (DVT) login to view 3 more bullets Prognosis natural history delays in diagnosis and management can lead to devastating lifelong impairment login to view 2 more bullets even with early surgery, neurologic recovery is variable long-term urinary dysfunction is common prognostic variables presence of saddle anesthesia or bladder dysfunction is associated with worse outcomes surgical decompression after 48 hours is associated with worse outcomes Anatomy Spinal cord conus medullaris tapered, terminal end of the spinal cord terminates at the T12 or L1 vertebral body filum terminale non-neural, fibrous extension of the conus medullaris that attaches to the coccyx cauda equina (horse's tail) collection of L1-S5 peripheral nerves within the lumbar canal compression is considered to cause lower motor neuron lesions login to view 2 more bullets Bladder receives innervation from parasympathetic nervous system (pelvic splanchnic nerves and the inferior hypogastric plexus) login to view 3 more bullets sympathetic plexus (hypogastric plexus) login to view 3 more bullets external sphincter of the bladder is controlled by the pudendal nerve voluntary control lower motor neuron lesions of cauda equina can interrupt the nerves forming the bladder reflex arcs unable to sense bladder filling unable to initiate appropriate muscle contraction and relaxation Classification Bladder function classification incomplete loss of urgency or decreased urinary sensation, but no incontinence or retention complete clear urinary and/or bowel retention or incontinence Presentation History may have a history of lifting a heavy object with lumbar spine in a flexed position ask about use of anticoagulation (hematoma), recent invasive procedures (hematoma), and IV drug use (infection) Symptoms common back pain (most common) login to view 1 more bullet unilateral or bilateral leg pain (second most common) unilateral or bilateral sensory changes in legs unilateral or bilateral motor weakness in legs saddle anesthesia login to view 2 more bullets bladder dysfunction login to view 2 more bullets rare sexual dysfunction (impotence in men) bowel dysfunction Physical exam inspection patient in distress due to low back pain, leg pain, and weakness palpation low back pain/tenderness is not a distinguishing feature palpation of the bladder to assess for urinary retention neurologic motor login to view 2 more bullets sensory login to view 3 more bullets reflex login to view 1 more bullet provocative tests diminished or absent bulbocavernosus reflex diminished or absent anal wink reflex login to view 1 more bullet Imaging Radiographs indications if high suspicion of CES, MRI is the study of choice radiographs can be obtained, but the process of obtaining an MRI should be initiated immediately recommended views AP and lateral findings usually normal (most common cause is lumbar disc herniation) may see other causes of spinal canal stenosis login to view 2 more bullets MRI indications study of choice to evaluate neurologic compression login to view 1 more bullet ideally obtained within 1-2 hours of presentation to ER findings often reveals large central disc herniation with complete spinal canal obliteration presence of spinal stenosis epidural hematoma epidural abscess CT myelography indications study of choice if patient is unable to undergo MRI (pacemaker, MRI-incompatible implants) findings sagittal and axial reconstructions can reveal space-occupying lesion partial or complete blockage of contrast Studies Laboratory CBC, ESR, and CRP concern for infectious etiology (epidural abscess) Urodynamic studies preoperative post-void residual volumes (PVR) recommended to be obtained prior to decompression, but not at the expense of delaying decompression normal post-void residual volume is <50-100 mL login to view 1 more bullet postoperative post-void residual volume assessment for return of bladder function DIAGNOSIS Key differential conus medullaris syndrome spinal cord infarct myelopathy Diagnosis diagnosis of cauda equina syndrome is made based on history, symptoms, and physical examination MRI imaging confirms the cause of the CES and is critical for surgical planning Treatment Operative emergent surgical decompression indications login to view 1 more bullet timing login to view 3 more bullets techniques login to view 3 more bullets outcomes login to view 5 more bullets Techniques Microdiscectomy (unilateral laminotomy, medial facetectomy, and discectomy) indications massive soft disc herniation in a younger patient with minimal degenerative changes approach 2 cm midline (or slightly paramedian) incision is made on one side of pathology expose lamina from spinous process to facet joint laminotomy 5-10 mm laminotomy made over the area of disc herniation medial facetectomy minimal facetectomy made with Kerrison rongeur ligamentum flavum window cleft in ligamentum flavum made, and lateral section removed annulotomy dural retraction removal of herniated disc material login to view 3 more bullets Laminectomy (bilateral laminectomy and medial facetectomy) indications older patient with degenerative changes including hypertrophic ligamentum flavum and lateral recess stenosis approach preservation of spinous process and PLC login to view 2 more bullets spinous process (and PLC) resection login to view 1 more bullet technique login to view 4 more bullets advantages login to view 5 more bullets Laminectomy and fusion indications high-grade spondylolisthesis insidious-type cauda equina syndrome in the context of degenerative spondylolisthesis Complications Nonoperative sexual dysfunction risk factors login to view 1 more bullet prognosis login to view 2 more bullets urinary dysfunction risk factors login to view 1 more bullet treatment login to view 1 more bullet chronic pain persistent leg weakness Operative dural tear incidence login to view 1 more bullet treatment login to view 5 more bullets iatrogenic segmental instability occurs with overlying aggressive medial facetectomy epidural fibrosis (scarring) cause of postoperative back and leg pain login to view 1 more bullet treatment login to view 3 more bullets wound infection incidence login to view 1 more bullet risk factors login to view 1 more bullet vascular injury incidence login to view 1 more bullet risk factors login to view 1 more bullet treatment login to view 2 more bullets