Nerve lesions and entrapment neuropathies of the lower limb

The main symptom of pressure on nerves is paraesthesia. Depending on the level of the compression, paraesthesia is accompanied by pain and numbness. The combination of these three symptoms and their interrelation are of importance in localizing the site of compression. Pressure on the distal spinal cord induces painless pins and needles in both feet, soon followed by numbness, incoordination and abnormal reflexes. This mechanism has been discussed in the chapters on the cervical and thoracic spine. Pressure on a nerve root causes segmental pain, paraesthesia at the distal aspect of the respective dermatome and, if the pressure increases, motor and sensory deficit. For detailed descriptions of these pathologies, see the chapters on the lumbar spine. Pressure on the lumbosacral plexus causes little pain but increasing numbness and weakness. For instance, compression of the plexus by a neoplasm does not cause pain in the limbs but only sacral or coccygeal pain. However, it does give rise to gross weakness of the muscles of one or both legs and feet. The effects of pressure on the peripheral nerves of leg and foot are discussed in this chapter.