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BSMS204 Theme 2 Musculoskeletal > 18. Lower limb nerve injuries > Flashcards

18. Lower limb nerve injuries Flashcards

1
Q

Cauda equina vs conus lesions

A

Conus medullaris - upper motor neuron L1/2 mix Cauda equina - lower motor neuron

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2
Q

Landmarks for lumbar puncture

A
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3
Q

Cauda equina vs conus medullaris

A
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4
Q

Cauda equina causes

A

Disc herniation, spinal fracture, tumour

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5
Q

Conus medullaris infections

A

Disc herniation, tumour

Inflammatory conditions

  • chronic inflammatory demyelinating polyradiculopathy
  • Sarcoidosis

Infection

  • CMV, HSV, EBV, Lyme, TB
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6
Q

L5/S1 disc herniation effect

A

Compression of cauda equina

Deformity of thecal sac impinging on the cauda equina

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7
Q

Nerve root entrapment - sciatica

A

Compression:

  • Disc -posterior central
  • Lateral Bone- osteophyte
  • Ligaments
  • Small canal- stenosis

Sciatica – usually L5, S1 n. root impingement

  • L5 n. root – exits between L5/ S1 vertebral bodies
  • S1 n. root exits between S1 / S2 vertebral bodies

Pain may be felt in dermatome (sharp/ superficial) or myotome (deep ache)

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8
Q

Lower limb root lesions - reflex and sensory loss (dermatomes)

A
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9
Q

Lower limb root lesions - weakness

A
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10
Q

Lumbar plexus

A
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11
Q

Sacral plexus

A
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12
Q

Lumbrosacral plexus regions

A

Childbirth (large head, prolonged labour)- esp obturator n., numbness inner thigh, pudendal n

Structural

  • Haematoma (on Warfarin)
  • Abscess
  • Malignanc
  • infiltration
  • Trauma

Non structural

  • Inflammatory
  • Diabetes
  • Vasculitis
  • Radiotherapy
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13
Q

Femoral nerve organisation

A

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

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14
Q

Femoral/lateral cutaneous nerves

A

Femoral N. Weakness

Hip flexion (iliacus)

Knee Extension

Loss of Knee Jerk

Can’t do stairs

Difficulty standing from seated Up stairs, knee buckling

Sensory loss Lat Cut. N. Thigh (relief if seated)

Sensory loss Femoral N

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15
Q

Femoral nerve damage

A
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16
Q

Sciatica

A

Pain in sciatic n. distrib (from buttock down leg and can go as far as feet and toes)

Nerve root entrapment (usually L5 / S1)

Differential diagnosis: Hip – pain may radiate not below knee Sacroiliac joints

Causes: Trauma, Haematoma Rarely sciatic nerve compression per se (Piriformis synd) Or misplaced IM injections

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17
Q

Piriformis syndrome

A

Controversial as to whether muscle compression per se can cause tingling in buttock and down leg (eg after exercise or straining, or prolonged sitting)

Probably may rarely occur in those with anatomical predisposition.

No consensus on criteria Diagnosis of exclusion

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18
Q

Sciatic nerve injury

A

Apart from:

  • Hip flexion
  • Knee extension
  • Hip adduction

Sciatic nerve or its branches, are motor to virtually all other muscle groups in the leg

Isolated Hip fracture – sciatic n. Pelvic/ sacral fracture – sacral plexus)

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19
Q

What can sciatic nerve damage look like?

A

Partial sciatic n. damage can look like Common peroneal or Tibial n. damage

20
Q

Tibial nerve

A

Behind knee

  • 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.

In the popliteal fossa the nerve gives off branches to gastrocnemius, popliteus, soleus and plantaris, and the sural nerve.

21
Q

Tibial N.- lower leg/ ankle

A

tibialis posterior, flexor digitorum longus, flexor hallucis longus Intrinsic foot muscles

Tarsal Tunnel

Sole pain worse standing/ walking Not heel pain Differential Morton’s neuroma

22
Q

Sural nerve

A
23
Q

Sural nerve - superficial, sensory

A

Used in nerve biopsies

Easy because superficial

doesnt give loss of function as only sensory

24
Q

Common peroneal nerve

A

May also be damaged by tight plaster casts, leg crossing

Weight loss- slimmers palsy

Sensory loss -dorsum of foot and outer aspect lower leg

Weakness of -dorsiflexion and eversion of foot

25
Q

Neurogenic foot drop

A
  • Upper motor neuron (brain/ spinal cord)
  • Conus
  • L4/L5
  • Cauda equina
  • Sacral plexus
  • Sciatic n.
  • Common peroneal n.
26
Q

Polyneuropathy

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

27
Q

Distribution of peripheral neuropathy

A
28
Q

Length dependent polyneuropathy

A

Common causes (Toxic/metabolic)

  • Diabetes
  • Alcohol
  • B12 def
  • Chemotherapy
  • Idiopathic

Clinical symptoms

  • Numbness, paraesthesia, weakness
  • Pain
29
Q

Non-length dependent polyneuropathy

A
30
Q

Guillian Barre syndrome

A

Named after French Neurologists in 2016

Also known as Acute inflammatory demyelinating polyneuropathy

Immune response to a preceding infection

Rapidly progressive (days to weeks) weakness including limbs, facial, respiratory and bulbar muscles

Absent reflexes

31
Q

Neuronopathy

A

Form of polyneuropathy

Disorders that affect specifically population of neurons.

Motor neuronopathy

  • Site of damage: Anterior horn cell
  • Causes: ALS, Polio

Sensory neuronopathy

  • Site of damage : Dorsal root ganglion
  • Causes: Sjogrens syndrome, Paraneoplastic
32
Q

Polyradiculopathy

A

Affects multiple nerve roots.

Causes:

  • Spinal stenosis: Cervical, lumbar
  • Cancer: Leptomeningeal metastases
  • Infection: Lyme, HIV,
33
Q

Types of peripheral neuropathy

A
34
Q

Shin splints

A

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)

35
Q

What is compartment syndrome?

A

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

36
Q

Where does CS occur?

A

Any limb compartment

Commonest Lower leg Forearm

Also Hand Foot

37
Q

why leg?

A
38
Q

What causes CS?

A

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

39
Q

Consequences of CS

A

Tissue perfusion is proportional to the difference between the capillary perfusion pressure and the interstitial fluid pressure

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

40
Q

Acute anterior CS leg

A

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

Deep peroneal nerve Sensation to the first dorsal web space

41
Q

Acute posterior CS leg

A
42
Q

What are the signs of CS?

A

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

43
Q

Investigation for compartment syndrome

A

Clinical suspicion is all important

Measuring of intra-compartmental pressures can be useful

Creatine kinase (CK) of 1000-5000 U/mL

Myoglobinuria

44
Q

Management of acute CS

A

Genuine confirmed CS is an emergency

Often surgery is required

Aim is to lay open the myofascial compartment and diminish intra-compartmental pressure

External causes

Tight casts/ splints Dressings

45
Q

Treatment of compartment syndrome

A

Fasciotomy

incision in skin and fascia to release pressure

vessels become no longer compressed, capillaries become functional

46
Q

Complications of management

A

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

Rhabdomyolysis - Renal Failure

Limb Loss

BSMS204 Theme 2 Musculoskeletal (22 decks)

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