Lower Limb Nerve Injuries Flashcards
1
Q
Where does the Lower motor neuron begin?
A
- at the Conus medularis
- L2
- at the Cauda aquina
2
Q
What is the difference between Conus medullaris and Cauda aquina syndromes?
A
-
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
3
Q
What causes Cauda equina syndrome?
A
- Disc herniation,
- spinal fracture,
- tumours
4
Q
What causes Conus medullaris syndrome?
A
- Disc herniation, tumour,
- Inflammatory conditions
- Infection
5
Q
Review the lower limb dermatomes and myotomes
L1-S5
A
6
Q
What action do lesions of the following roots affect?
L1-S1
A
- 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
7
Q
Where does the lateral cutaneous nerve originate from?
- what does it innervate
A
- originates from L2, L3
- innervates
- the sensation on the outer aspect of the thigh
8
Q
Where does the Obturator nerve originate from?
- what does it innervate
A
- originates from L3,L4
- innervates
- the medial compartment of the thigh
- the obturator muscle
- adducts the hips
9
Q
Where does the Femoral nerve originate from?
- what does it innervate
A
- originates from L2,L3,L4
- sensory and motor innervation to the leg
10
Q
Where does the Sciatic nerve originate from?
- branches?
A
- originates from L4,5,S1,2,3
- it has a fibular and tibial portion
11
Q
What are causes of Lumbosacral plexus lesions?
A
- 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
12
Q
What is the effect of femoral nerve lesions?
A
- 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
13
Q
What are causes of femoral nerve damage?
A
- pelvic fracture
- pregnancy
- gynae surgeries
- hysterectomy
- femoral bypass
14
Q
How would Femoral/Lateral cutaneous nerve lesions present?
A
- 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.)
15
Q
What is Sciatica?
- causes
- differentials
A
- 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
16
Q
What is Piriformis syndrome?
A
- compression of the sciatic nerve by the piriformis muscle
17
Q
What are causes of sciatic nerve injury?
A
- Isolated hip fracture
- Pelvic/sacral fracture - sacral plexus
18
Q
What is important to remember about the anatomy of the sciatic nerve in terms of injury?
A
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
19
Q
What is the effect of a Tibial nerve lesion
- causes?
- presentation
A
- 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 )
20
Q
What is the presentation of Common peroneal (fibular) nerve lesion?
- cause
A
- 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
21
Q
What are causes of Neurogenic Foot drop?
A
- Upper motor neuron (brain/ spinal cord)
- Conus
- L4/L5
- Cauda equina
- Sacral plexus
- Sciatic n.
- Common peroneal n
22
Q
What is Polyneuropathy and Peripheral neuropathy?
A
- 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
23
Q
What are common causes of Length dependent polyneuropathy
- clinical symptoms
A
- Common causes (Toxic/metabolic causes)
- Diabetes
- Alcohol
- B12 def
- Chemotherapy
- Idiopathic
- Clinical symptoms
- Numbness, paraesthesia, weakness
- Pain (small fibres)
24
Q
What is non-length dependent polyneuropathy?
A
- referes to a demyelinating syndrome
- Guillian-Barré sundrome
25
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
26
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
27
What is Polyradiculopathy?
- causes
* syndrome that affects multiple nerve roots.
* Caused by:
* Spinal stenosis: Cervical, lumbar
* Cancer: Leptomeningeal metastases
* Infection: Lyme, HIV,
28
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
29
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
30
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
31
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
32
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
33
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
34
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
35
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
36
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
