UMN lesions vs LMN lesions Flashcards
What signs indicate UMN lesion?
- Increased tone
- Spasticity
- Weakness
- Brisk reflexes, upgoing Babinski
What signs indicate LMN lesion?
- Wasting and fasciculation
- Decreased tone
- Weakness
- Reduced reflexes
What are the potential causes of unilateral UMN lesions (pyramidal weakness)?
Brain → Cord
- Intracranial: stroke, SOL → hemisensory loss
- Brainstem: stroke, SOL → may be crossed signs
- Spinal cord: MS, infarct/haemorrhage, SOL, disc prolapse, trauma, syringomyelia, congenital → sensory level/segmental sensory loss
What are the potential causes of bilateral UMN lesions (pyramidal weakness)?
3 Ms
- MS
- Motor neurone disease → normal sensation
- Myelopathy: cord compression (e.g. due to cervical myelopathy, SOL, disc prolapse, paraspinal infection), trauma, transverse myelitis, syringomyelia, congenital → sensory level/segmental sensory loss
Others:
- Brainstem stroke
- Hereditary spastic paraplegia
- Cerebral palsy
- HTLV-1
- Syphilis
What are the features of radiculopathy?
Dermatomal sensory loss
What are the causes of radiculopathy?
- Disc herniation/ degenerative disc disease
- Spondylosis
- OA with osteophytes
What is the general feature of plexopathies?
Vast dermatomal sensory loss
What are the causes of brachial plexopathy?
- Brachial neuritis
- Trauma (dislocated shoulder)
- Congenital (Erb’s palsy, Klumpke’s)
- Thoracic outlet syndrome
- Neoplastic infiltration/compression
- Radiotherapy
What are the causes of lumbosacral plexopathy?
- Trauma
- Congenital
- Neoplastic infiltration/compression
- Radiotherapy
What are the potential causes of median nerve palsy?
- Carpal tunnel syndrome
- Distal radius fracture
- Penetrating forearm injuries
- Pronator teres syndrome
What are the potential causes of carpal tunnel syndrome?
- Idiopathic
- Pregnancy
- Obesity
- Local pressure
- Hypothyroidism
- Acromegaly
- Diabetes
What are the potential causes of ulnar nerve palsy?
- Compression at elbow/cubital tunnel
- Fractures
- Guyon’s canal/ulnar tunnel syndrome
What are the potential causes of radial nerve palsy?
- Trauma/compression at axilla (crutches, Saturday night palsy, stabbing)
- Fracture to mid-humerus
- Elbow fracture/dislocation/ganglion
What are the potential causes of axillary nerve palsy?
- Shoulder dislocation
- Fracture at surgical neck of humerus
What are the potential causes of common peroneal nerve palsy?
- Plaster cast compression
- Trauma
What are the potential causes of bilateral LMN lesions (distal weakness) associated with abnormal sensation?
Sensorimotor polyneuropathy: ABCDE
- Alcohol
- B12/thiamine (B1) deficiency
- Charcot-Marie-Tooth, Carcinomas
- Diabetes, drugs (TB drugs, metronidazole, nitrofurantoin, vincristine, cisplatin, amiodarone)
- Every vasculitis (SLE, RA, polyarteritis nodosa) and some infections (HSV, HIV, leprosy, syphilis)
What are the potential causes of bilateral LMN lesions (distal weakness) associated with normal sensation?
Distal motor neuropathy
- Chronic inflammatory demyelinating polyneuropathy
- Myotonic dystrophy
- Inclusion body myositis (proximal in legs, distal in arms)
- Progressive muscular atrophy
- Lead poisoning
- Porphyria
What are the potential causes of acute flaccid paralysis?
- GBS
- Some rare infections (e.g. rabies, polio, West Nile virus)
- Cauda equina
- Spinal cord shock
What are the potential causes of proximal weakness and normal sensation?
DENIM:
- Dystrophies: Becker’s/Duchenne, limb girdle, fascioscapulohumeral
- Endocrinological: Cushing’s syndrome, hyper/hypothyroidism, diabetic amyotrophy (lower limbs)
- Neuromuscular: MG, Lambert-Eaton syndrome
- Inflammatory: dermato-/polymyositis, inclusions body myositis
Metabolic/congenital/ mitochondrial myopathies
What are the causes of mononeuritis multiplex?
- Vasculitis:
- granulomatosis with polyangiitis
- eosinophilic granulomatosis
- polyarteritis nodosa
- microscopic polyangiitis - Autoimmune:
- RA
- SLE
- Cryoglobulinaemia
- Sjogren’s syndrome - Infectious:
- Lyme disease
- HIV
- Leprosy - Others:
- Diabetes mellitus
- Amyloidosis
- Sarcoidosis
What are the causes of mixed UMN and LMN signs?
- MND (no sensory deficit)
- Dual pathology: cervical myelopathy + polyneuropathy)
- Myeloradiculopathy
- Subacute combined degeneration of the cord (symmetrical UMN signs with absent reflexed, impaired posterior columns function, peripheral sensory neuropathy)
