Nervous system Flashcards
Upper motor neuron (UMN) lesion where does weakness develop?
Develops in the weaker muscle groups. The extensors in the arms and flexors in the legs.
UMN lesion - where does spactisity develop and how does it manifest?
Spasticity develops in the stronger muscle groups (arm flexors and leg extensors). It manifests as increased tone that is velocity-dependent, ie the faster you move the patient’s muscle, the greater the resistance, until it finally gives way (like a ‘clasp-knife’).
UMN lesion muscle wasting
Less prominent
UMN lesion reflexes
- There is hyperreflexia: reflexes are brisk
- Plantars are upgoing (+ve Babinski sign)
- ± clonus (elicited by rapidly dorsiflexing the foot; ≤3 rhythmic, downward beats of the foot are normal)
UMN lesion fine motor skills
Loss of skilled fine finger movements may be greater than expected from the overall grade of weakness.
Where do lower motor neurone (LMN) lesions exist?
Anywhere from the anterior horn cells distally, including the nerve roots, plexuses, and peripheral nerves.
LMN lesion pattern of weakness
The pattern of weakness corresponds to the muscles supplied by the involved neurons.
LMN lesion muscle wasting
Affected muscles show wasting ± fasciculation
LMN lesion tone
There is hypotonia/flaccidity: the limb feels soft and floppy, providing little resistance to passive stretch.
LMN lesion reflexes
Reflexes are reduced or absent; the plantars remain flexor.
Muscle weakness grading (MRC classification)
- Grade 0 - No muscle contraction
- Grade 1 - Flicker of contraction
- Grade 2 -Some active movement
- Grade 3 - Active movement against gravity
- Grade 4 - Active movement against resistance
- Grade5 - Normal power (allowing for age)
Questions to ask about headaches
- Onset
- Character
- Frequency
- Duration
- Associated features
- Precipitating cause
- Drug history
- Social history
Rapid onset headache differential diagnosis
- Subarachnoid haemorrhage
- Meningitis
- Encephalitis
- Post-coital headache
Symptoms of subarachnoid haemorrhage
- sudden-onset
- ‘worst ever’ headache
- often occipital
- stiff neck
- focal signs
- decreased consciousness
Character - tight band
Think tension headache
Character - throbbing/pulsatile/lateralising
Migraine
What do recurring headaches suggest?
Headaches that recur tend to be benign.
- Migraine
- Cluster headache
- Trigeminal neuralgia
- Recurrent meningitis
Why is drug history important in headaches?
Exclude medication overuse (analgesic rebound) headache: Culprits are mixed analgesics (paracetamol+codeine/opiates), ergotamine, and triptans.
Symptoms of cluster headaches
- Rapid-onset of excruciating pain around one eye that may become watery and bloodshot with lid swelling, lacrimation, facial flushing, rhinorrhoea, miosis ± ptosis (20% of attacks)
- Pain is strictly unilateral and almost always affects the same side
- It lasts 15–180min, occurs once or twice a day, and is often nocturnal
- Clusters last 4–12wks and are followed by pain-free periods of months or even 1–2yrs before the next cluster
Cluster headache treatment
- Acute
- give 100% O2 for ~15min via non-rebreathable mask (not if COPD)
- sumatriptan SC 6mg at onset
- Preventative
- avoid triggers
- corticosteroids (short term only)
- verapamil
- lithium
