Cauda equina
Spinal cord ends T10-L1, where nerve roots are constituted. They then course down in the intraspinal canal until exiting in foramina.
Lumbar spinal stenosis - chronic compression due to anatomic abnormality - disc herniation / ligamentum flava thickening / spondylosis / spondylolisthesis
Presentation of LSS - neurogenic claudication, worse with extension at hip, relieved with flexion.
Cauda equina - presentation
[edit | edit source]bilateral leg weakness in L3 - S1 distributions
- Bladder dysfunction (retention and overflow incontinence)
- Bowel incontinence
- Saddle anaesthesia
Lumbosacral myotomes
[edit | edit source]| L1 |
| Femoral nerve |
| Iliopsoas (hip flexion) |
| L2 |
| Femoral nerve |
| Iliopsoas (hip flexion) |
| Quadriceps (knee extension) |
| Obturator nerve |
| Hip adductors |
| L3 |
| Femoral nerve |
| Iliopsoas (hip flexion) |
| Quadriceps (knee extension) |
| Obturator nerve |
| Hip adductors |
| L4 |
| Femoral nerve |
| Iliopsoas (hip flexion) |
| Quadriceps (knee extension) |
| Obturator nerve |
| Hip adductors |
| L5 |
| Peroneal nerve |
| Ankle dorsiflexion (tibialis anterior) |
| Ankle eversion (peroneus muscles) |
| Tibial nerve |
| Ankle inversion (tibialis posterior) |
| Superior gluteal nerve |
| Hip abduction (gluteus medius) |
| Leg internal rotation (tensor fascia latae) |
| S1 |
| Inferior gluteal nerve |
| Hip extension (gluteus maximus) |
| Sciatic nerve |
| Knee flexion (hamstrings) |
| Tibial nerve |
| Ankle plantar flexion |
| S2 |
| Inferior gluteal nerve |
| Hip extension (Gluteus maximus) |
| Sciatic nerve |
| Knee flexion (hamstrings) |
| Tibial nerve |
| Ankle plantar flexion |
Although there are classic descriptions for the distributions of myotomes and dermatomes, substantial variability exists in these distributions from person to person [7,8]. Sensory fields have considerable overlap, but there are areas that are exclusively served by individual nerves. These areas are called autonomous zones. The most important of these in the evaluation of lumbosacral radiculopathies include the sole of the foot (S1), dorsum of the foot (L5), medial calf (L4), and anterior thigh (L2 and 3) [9].
We recommend urgent neuroimaging in the initial assessment for patients with any of the following conditions [1]:
●Acute radiculopathy with progressive neurologic deficits
●Radiculopathy with urinary retention, saddle anesthesia, or bilateral neurologic symptoms or signs
●Suspected neoplasm
●Suspected epidural abscess