Lower limb nerve injuries and compartment syndrome Flashcards
Pain severity
Cauda equina
- radicular
- more severe
Conus medullaris
- less severe
Location of pain
Cauda equina
- unilateral/ asymmetric
- perineum, thighs and legs
Conus medullaris
- bilateral
- perineum, thighs
Sensory disturbance
Cauda equina
- saddle
- unilateral/ asymmetric
Conus medullaris
- bilateral saddle distribution
Motor loss
Cauda equina
- asymmetric
- atrophy
Conus medullaris
- symmetric
Reflexes
Cauda equina
- ankle and knee reduced
Conus medullaris
- ankle only reduced
Bowel/ bladder
Cauda equina
- late
Conus medullaris
- early
Sexual function
Cauda equina
- impaired- less severe
Conus medullaris
- impaired- more severe
Causes of pain
Cauda equina
- disc herniation, spinal fracture, tumours
Conus medullaris
- disc herniation, tumour
- inflammatory conditions (chronic inflammatory demyelinating, polyradiculopathy, sarcoidosis)
- infection (CMV, HSV, EBV, lyme, TB)
Nerve root entrapment- ‘sciatica’
Compression
- disc: posterior central, lateral
- bone: osteophyte
- ligaments
- small canal: stenosis
Sciatica- usually L5, S1 nerve root impingement
Pain may be felt in dermatome (sharp/ superficial) or myotome (deep ache)
Lower limb root lesions- reflex and sensory loss
Lower limb dermatome more variable than upper limb
L1 inguinal area L2 front of thigh L3 front of knee L4 from- inner/ medial leg L5 outer leg, dorsum of foot, inner sole S1 little toe, rest of sole, back of leg S2 thigh to top of buttock S3-5 concentric rings around anus/ genitalia
Knee jerk L4
Ankle jerk S1
Lower limb root lesions- weakness
L1/2- hip flexion
L3/4- knee extension
L4- foot inversion
L5- knee flexion, ankle dorsiflexion, toe extension, foot inversion and eversion
S1- knee flexion, ankle plantar flexion, toe flexion, foot eversion
Lumbosacral plexus lesions
Childbirth (large head, prolonged labour)- esp obturator, numbness inner thigh, pudendal nerve
Structural
- haematoma
- abscess
- malignancy
- trauma
Non structural
- inflammatory
- diabetes
- vasculitis
- radiotherapy
Femoral nerve organisation
Hip flexors, iliopsoas affected if proximal damage (above inguinal ligament)
Only knee extension if below inguinal ligament
Distal lesion may produce a pure motor or pure sensory syndrome
Femoral/ lateral cutaneous nerves
Femoral nerve weakness Hip flexion Knee extension Loss of knee jerk Can't do stairs
Sensory loss- femoral nerve
Saphenous (sensory branch of femoral nerve)
Femoral nerve damage
Surgery
Gynae procedures, esp hysterectomy, femoral artery bypass/ puncture
Sciatica
Pain in sciatic nerve distribution
Nerve root entrapment (usually L5/S1)
Differential diagnosis of sciatica
Hip- pain may radiate, not below knee
Sacroiliac joints
Causes of sciatica
Trauma
Haematoma
Rarely sciatic nerve compression
Misplaced IM injections
Piriformis syndrome
Controversial as to whether muscle compression can cause tingling in buttock and down leg
Probably may rarely occur in those with anatomical predisposition
Diagnosis of exclusion
Sciatic nerve injury
Apart from hip flexion, knee extension, hip adduction
Scaitic nerve or its branches are motor to virtually all other muscle groups in the leg
Isolated hip fracture- sciatic nerve
Pelvic/ sacral fracture- sacral plexus
Tibial nerve- behind knee
Can’t stand on tiptoes
Weak foot inversion
Painful numb sole
Causes
- trauma: haemorrhage
- bakers cyst
- nerve tumour
- antrapment by the tendinous arch at the soleus muscle
Tibial nerve- lower leg/ ankle
Sole pain worse standing/ walking
Not heel pain
Differential morton’s neuroma
Common peroneal nerve
May also be damaged by tight plaster casts, leg crossing, weight loss (slimmers palsy)
Sensory loss- dorsum of foot and outer aspect of lower leg
Weakness of- dorsiflexion and eversion of foot
Neurogenic foot drop
Upper motor neuron
Conus
L4/L5
Cauda equina
Sacral plexus
Sciatic nerve
Common peroneal nerve
Polyneuropathy
Generalised relatively homogenous process affecting many peripheral nerves with the distal nerves affected most prominently
Length dependent polyneuropathy
Common causes
- diabetes
- alcohol
- B12 deficiency
- chemotherapy
- idiopathic
Clinical symptoms
- numbness, paraesthesia, weakness
- pain
Guillain barre syndrome
Acute inflammatory demyelinating polyneuropathy
Immune response to a preceding infection
Rapidly progressive weakkness including limbs, facial, respiratory and bulbar muscles
Absent reflexes
Neuronopathy
Form of polyneuropathy
Disorders that affect specifically population of neurons
Motor neuropathy
- sites of damage: anterior horn cell
- causes: ALS, polio
Sensory neuronopathy
- site of damage: dorsal root ganglion
- causes: sjogrens syndrome, paraneoplastic
Polyradiculopathy
Affects multiple nerve roots
Causes
- spinal stenosis: cervical, lumbar
- cancer: leptomeningeal metastases
- infection: lyme, HIV
Shin splints
Muscle bulk increases 20% during exercise and contributes to the transient increase in intracompartmental pressure
Anterior and lateral compartments of the lower leg are commonly affected
Generally causes pain on and post exercise- shin splints
Manage with RICE
Compartment syndrome
Increase in pressure within a myofascial compartment which has limited ability to expand
May be acute or chronic
Acute compartment syndrome is a surgical emergency
Where does compartment syndrome occur?
Any limb compartment
Commonest
- lower leg
- forearm
What causes compartment syndrome?
Fractures (1-6% tibial fractures)
Crush injuries
Burns
Electric shock
Fluid injection
Drugs
Disease
External causes
Consequences of compartment syndrome- physiology
Tissue perfusion is proportional to the difference between the capillary perfusion pressure and the interstitial fluid pressure
Elevated compartment pressure causes muscle and nerve ischaemia
Consequences of compartment syndrome- pathology
Untreated, within 6-10 hours, the final result is muscle infarction, tissue necrosis, and nerve injury
Certain tissues are more sensitive than other and this can be a clue to diagnosis
Acute anterior compartment syndrome leg
Dorsiflexion muscles of ankle and foot
- tibialis anterior
- extensor digitorum longus
- extensor hallucis longus
- peroneus tertius
Anterior tibial artery
- commonly injured in lateral tibial plateau fractures
Depp peroneal nerve
- sensation to the first dorsal web space
Acute posterior compartment syndrome leg
Superficial posterior
Plantar flexors of foot
- gastrocnemius
- plantaris
- soleus
Sural nerve
- sensation to lateral aspect of the foot and distal calf
What are the signs of compartment syndrome?
Pain (out of proportion to the original injury)
Pain on passive stretching
Tense limb
Decreased function of the compartment muscles
Distal neurologic compromise
Reduced distal pulses
Investigations for compartment syndrome
Measuring of intra-compartmental pressures can be useful
Creatine kinase of 1000-5000 U/ml
Myoglobinuria
Management of acute compartment syndrome
Genuine confirmed CS is an emergency
Often surgery is required
Aim is to lay open the myofascial compartment and diminish intra-compartmental pressure
