Intro to LMN disorders Flashcards
68 yr man , no PMH
- difficult rising from chair initially , worsening over past 12 months
- difficult reaching up from shelves , grasping objects for 6 months
- no pain
- no sensory loss
Examination :
- intact cranial nerves
- intact/reduced reflexes
- MRC grade 4 power in upper limbs , 4 elbow extension/flexion , 4 wrist flexion , 5 wrist extension , 3 finder flexion
- 3 hip flexion , 4 knee extension , 4 ankle dorsiflexion
- thigh muscles atrophied but normal muscle bulk otherwise
- no fasciculation
What type of disorder could it be ?
Myopathy ( body myositis )
Reason : symmetrical predominantly proximal weakness with no sensory loss and spared reflexes
36 woman
- 6w of double vision , initially on left lateral. gaze now in all directions
- eyelids tend to close throughout day
- speech nasal and hoarse for 3w
- difficult swallowing some food for 3 w ( bread/steak)
- difficult to climb stair or use hairdryers for 2w
- exercise tolerance reduces , SOB on minimal exertion and chest heaviness when lying flat
on Examination :
- bilateral ptosis R>L - fluctuates
- external opthalmoplegia that fatigues on examination
- weakness of eye and lip closure
- weak tongue movements
- speech is slurred and nasal
- 4 weakness of shoulder abduction and hip flexion , fatigues on RNS
- normal reflex, sensation and no wasting
What is the problem
Myasthenia Gravis ( neuromuscular junction disorder ) Reason : fatiguable proximal and symmetrical weakness + extra-ocular, facial and bulbar weakness
18 male
- 8 y history of tripping when walking , progressively worse
- difficulty writing for 6months
- never good at sports but met normal motor milestones
- funny feet needing insoles ( same with mother and grandmother )
- denies sensory symptoms
- gets cramps in hand and feet
On examination :
- normal Cranial nerves
- distal lower limb wasting , mild hand wasting
- no fasiculations
- deformed feet: high feet with callous formation
- UL power: 4 wrist extension , 4 wrist felxion , 3 finger extension , 4 finger flexion , 5 everywhere else
- LL power: 4 hip flexion , 4 knee flexion/extension , 4 ankle plantar flexion , 4 ankle dorsiflexion
- sensation : reduced pinprick and temperature below knees bilaterally
- globally absent reflexes
What is the problem
Peripheral neuropathy ( Charcot Marie tooth ) Reason: symmetrical distal weakness and wasting with absent reflexes and some sensory impairment
65 woman
- difficulty using left arm for 6 months
- left leg started to drag 4 months
- speech changed , family struggle to make her out
- food getting stuck in through for 3 months
- losing weight rapidly
- sleep interrupted frequently , early morning headache , doesn’t feel refreshed
On examination :
- cachectic
- UL : left bicep and tricep wasting with fasiculations
- LL : left gastrocnemius wasted and fasiculations , right and left quads wasted
- Cranial nerves : normal eye movements , no ptosis , eye closure mildly weak , lip closure very weak , tongue wasted and fasiculation , very dysarthric speech
- 4 neck extension
- Reflexes: biceps jerk on right absent , ankle jerk on left absent , other reflexes are brisk
- left upgoing plantar response
- intact sensation
- UL power : Left more reduced than right
- LL power: Left more reduced than Right
What is the problem
Motor neurone disease
- Reasons : symptoms of respiratory muscle weakness ( not feeling refreshed, waking up ) , painless progressive weakness and wasting over long period of time , asymmetric with bulbar involvement and UMN signs
UMN vs LMN presentation
UMN : no wasting , hypertonia , hyperreflexia , hyper plantar response
LMN : wasting ( early) , no increase in tone or reduced, reflexes lost or reduced, no plantar response
LMN starts where ?
Anterior horn cell in spinal cord
what is myopathy
Problem with muscle fibres
What is neuropathy
Problem with peripheral nerve
What is radiuclopathy
Problem with nerve root
What is myasthenia
Problem in neuromuscular junction
Pattern of weakness expected in myopathies
proximal weakness ( difficult standing up . Sitting )
- symmetrical weakness
- can be painful
- reflexes spared until later on with chronic myopathies , then reduced or lost
- some muscle wasting, but most happens later on in the disorder
Neuromuscular junction disorders presentation
- fatiguability : fluctuating weakness in muscles
- extra ocular muscles affected: ophthalmoplegia , ptosis , diplopia
- bulbar muscles affected: chewing, swallowing , speech , neck movement
Most common neuromuscular junction disorder
Myasthenia Gravis
What is polyneuropathy
Diffuse disorder of peripheral nerves ( damaged all the nerves )
What is mononeuropathy and give examples
Single peripheral nerve , ex: carpal tunnel syndrome with median nerve , common peritoneal nerve ( all due to entrapment of nerve )
What is mono neuritis multiplex
Several individual nerves are affected one after another, presenting step wise and then leading to weakness eventually
Presentation of polyneuropathies
- length dependent weakness - longest nerves in body are affected first , usually starts in feet ( distal )
- symmetrical
- Weakness and maybe sensory loss
- absent reflexes
- distal Wasting - pes cavus
What is motor neurone disease
- Degeneration of cortical pyramidal cells , portico-spinal pathways , brain stem motor nuclei and anterior horn cells
- painless progressive weakness and wasting
- normal eye movements
- normal sensation
- Combination of UMN and LMN signs
What could indicate proximal muscle weakness
Difficulty with stairs , brushing hair
what could indicate distal weakness
Tripping , difficulty opening jars/buttons
History for LMN
- pattern of weakness : distal or proximal
- How quickly weakness came on : years ( genetic ) , acute ( infectious/inflammatory )
- Is weakness painful : might be muscle disease, peripheral neuropathy , think radiuclopathy
- Is there sensory loss : might be radiuclopathy or peripheral neuropathies
- Symptoms of respiratory muscle weakness
On examination if there is very prominent wasting what might be the cause
MND or peripheral neuropathies
fasciculation’s on examination could indicate what
Very Proximal lesion or MND
If sensory loss is present what is rolled out
Myopathy , MND and myasthenia
absent or reduced reflex indicate what
Peripheral neuropathy
reduced or normal reflexes indicate what
Myopathy
increased reflexes , despite LMN signs indicates what
Motor neurone Disease ( MND )
Trendelenberg/waddling gait may indicate what
Myopathy
foot drop , high stoppage gat indicates what
peripheral neuropathy
Investigations for LMN lesions
- Bloods
- Creatine kinase: in all patient with neuromuscular weakness
- Neurophysiology : electrical stimulation of muscles and nerves
- Muscle biopsy : or nerve
- MRI spine to exclude other causes
- Muscle MRI : reveals specific pattern of muscle wasting
- Genetic testing
If CK levels over 10,000 what does it indicate
Rhabdomyolysis , muscular dystrophy
Denervation levels of CK
500-1000
what patients will have naturally higher CK
Black patients
What is EMG
Electromyography: needle inserted into muscle to detect muscle activity at rest and with contraction to see damage to muscle asa result of myopathy or denervation
what test would you do to see how nerve conducts motor response
Nerve conduction studies
What can muscle biopsy help differentiate
Myopathies vs neuropathies
