Lower Limb Nerve Injuries Flashcards
Where does the Lower motor neuron begin?
- at the Conus medularis
- L2
- at the Cauda aquina
What is the difference between Conus medullaris and Cauda aquina syndromes?
-
cauda aquina pain radiates and is more severe
- it’s unilateral/ asymmetric pain of the perineum, thighs and legs
- asymmetrical motor loss
- ankle and knee reflexes reduced conus medullaris is only the ankle reflexes
- bowel symptoms are a later presentation
What causes Cauda equina syndrome?
- Disc herniation,
- spinal fracture,
- tumours
What causes Conus medullaris syndrome?
- Disc herniation, tumour,
- Inflammatory conditions
- Infection
Review the lower limb dermatomes and myotomes
L1-S5
What action do lesions of the following roots affect?
L1-S1
- 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 plantarflexion
- Toe flexion
- Foot eversion
Where does the lateral cutaneous nerve originate from?
- what does it innervate
- originates from L2, L3
- innervates
- the sensation on the outer aspect of the thigh
Where does the Obturator nerve originate from?
- what does it innervate
- originates from L3,L4
- innervates
- the medial compartment of the thigh
- the obturator muscle
- adducts the hips
Where does the Femoral nerve originate from?
- what does it innervate
- originates from L2,L3,L4
- sensory and motor innervation to the leg
Where does the Sciatic nerve originate from?
- branches?
- originates from L4,5,S1,2,3
- it has a fibular and tibial portion
What are causes of Lumbosacral plexus lesions?
- Childbirth (large head, prolonged labour)- esp obturator n., numbness inner thigh, pudendal n.
Structural
- Haematoma (on Warfarin)
- Abscess
- Malignancy
- Infiltration
- Trauma
Non-structural
- Inflammatory,
- Diabetes
- Vasculitis
- Radiotherap
What is the effect of femoral nerve lesions?
- Hip flexors, Iliopsoas affected if proximal damage (above inguinal Ligament)
- Only knee extension is effected if lesion is below inguinal ligament
- Distal lesion may produce a pure motor or pure sensory syndrome
What are causes of femoral nerve damage?
- pelvic fracture
- pregnancy
- gynae surgeries
- hysterectomy
- femoral bypass
How would Femoral/Lateral cutaneous nerve lesions present?
- difficulty doing stairs, or standing from a sitting position
- knee-buckling
- sensory loss or tingling on the lateral thigh (lat cut. n.)
- sensory loss or tingling on the medial thigh (Fem N.)
What is Sciatica?
- causes
- differentials
- Pain in sciatic n. distrib
- Nerve root entrapment (usually L5 / S1)
- Causes: Trauma, Haematoma Rarely sciatic nerve compression per se (Piriformis synd) Or misplaced IM injection
- Differential diagnosis: Hip – pain may radiate not below knee Sacroiliac joints
What is Piriformis syndrome?
- compression of the sciatic nerve by the piriformis muscle
What are causes of sciatic nerve injury?
- Isolated hip fracture
- Pelvic/sacral fracture - sacral plexus
What is important to remember about the anatomy of the sciatic nerve in terms of injury?
Partial sciatic n. damage can look like Common peroneal or Tibial n. damage, as the sciatic nerve has two branches. The issue might still be more proximal
What is the effect of a Tibial nerve lesion
- causes?
- presentation
- Can’t stand on tiptoes Weak foot inversion Painful numb sole
-
Causes:
- Trauma: Haemorrhage
- Bakers cyst
- Nerve tumour
- Entrapment by the tendinous arch at the soleus muscle
-
Presentation
- sole pain, worse when standing/ walking (no heel pain )
What is the presentation of Common peroneal (fibular) nerve lesion?
- cause
- Sensory loss -dorsum of foot and outer aspect lower leg
- Weakness of -dorsiflexion and eversion of foot
- causing foot drop
Cause
- Broken fibula
- tight plaster casts, leg crossing, Weight loss- slimmers palsy
What are causes of Neurogenic Foot drop?
- Upper motor neuron (brain/ spinal cord)
- Conus
- L4/L5
- Cauda equina
- Sacral plexus
- Sciatic n.
- Common peroneal n
What is Polyneuropathy and Peripheral neuropathy?
- Polyneuropathy – generalised relatively homogeneous process affecting many peripheral nerves with the distal nerves affected most prominently.
- Peripheral neuropathy – refers to any disorder of the peripheral nervous system including radiculopathies and mononeuropathies
What are common causes of Length dependent polyneuropathy
- clinical symptoms
- Common causes (Toxic/metabolic causes)
- Diabetes
- Alcohol
- B12 def
- Chemotherapy
- Idiopathic
- Clinical symptoms
- Numbness, paraesthesia, weakness
- Pain (small fibres)
What is non-length dependent polyneuropathy?
- referes to a demyelinating syndrome
- Guillian-Barré sundrome
What is Guillain Barre syndrome?
- Acute inflammatory demyelinating polyneuropathy
- Immune response to a preceding infection that effects the myelin sheath
- Rapidly progressive (days to weeks) weakness including limbs, facial, respiratory and bulbar muscles
- Absent reflexes
What is Neuronpathy?
- types (2)
- Form of polyneuropathy
- Disorders that affect specifically the population of neurons.
- Motor neuronopathy –
- Site of damage: Anterior horn cell
- Causes: ALS, Polio
- Sensory neuronopathy –
- Site of damage: Doral root ganglion
- Causes: Sjogrens syndrome, Paraneoplastic
What is Polyradiculopathy?
- causes
- syndrome that affects multiple nerve roots.
- Caused by:
- Spinal stenosis: Cervical, lumbar
- Cancer: Leptomeningeal metastases
- Infection: Lyme, HIV,
What are “Shin splints”
- causes
- presentation
- management
- Pain in the anterior or lateral part of the leg caused by:
- 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- AKA Shin Splints
- Manage with RICE (rest / cooling – ice
What is 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
What are the causes of compartment syndrome
(4 main groups) (TEDD)
Trauma
- Fractures (1-6% Tibial Fractures)
- Crush Injuries
- Burns
- Electric Shock
- Fluid Injection
Drugs
- Warfarin/other anticoagulants • Anabolic Steroid use • Iv drug use
Disease
- Haemophilia
External Causes
- Tight splints/casts • Tourniquet
What are the consequences of compartment syndrome?
- Tissue perfusion is proportional to the difference between the capillary perfusion pressure and the interstitial fluid pressure therefore elevated compartment pressure causes muscle and nerve ischemia
- Untreated, within 6-10 hours, the final result is muscle infarction, tissue necrosis, and nerve injury
- Certain tissues are more sensitive than others and this can be a clue to diagnosis
- Sensory nerves- numbness
Go through Acute anterior compartment syndrome in the legs
- muscles affected
- other structures affected?
- Dorsiflexion muscles of ankle and foot
- Tibialis anterior, Extensor digitorum longus Extensor hallucis longus, Peroneus tertius
- dorsiflexion causes pain
- Anterior tibial artery
- Commonly injured in lateral tibial plateau fractures
- Deep peroneal nerve
- Sensation to the first dorsal web space may be lost
Go through Acute posterior compartment syndrome in the legs
- muscles affected
- other structures affected?
- Superficial posterior Plantar flexors of foot
- Gastrocnemius, Plantaris, Soleus
- Sural nerve
- Sensation to the lateral aspect of the foot and distal calf
- if the foot is plantiflexed it causes pain
What are the signs of compartment syndrome?
(6)
- 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
What investigations can be done in suspected compartment syndrome?
- Clinical suspicion is all important
- Measuring of intra-compartmental pressures can be useful
- Creatine kinase (CK) of 1000-5000 U/mL Myoglobinuria
What is the treatment/management of compartment syndrome
- complications?
- Often surgery is required
- Aim is to lay open the myofascial compartment and diminish intra-compartmental pressure
- don’t forget to look for external causes Tight casts/ splints Dressing
- If fasciotomy is performed within 25-30 hours following onset of acute CS, the prognosis is good
- Little or no return of function can be expected when diagnosis and treatment are delayed
- can lead to Rhabdomyolysis –> renal failure
- Limb lose
