Neurolocalisation Flashcards
What are the clinical features if there is weakness at the cortex? What are some causes?
Cortical signs
- Aphasia: Difficulty with language
- Apraxia: difficulty with planning a motor function
- Agnosia: eg: Visual Agnosia
- Amnesia: Problems with memory
- Neglect
Human homunculus: uneven brachiocrural weakness (over representation of face, hand, thumb)
What are the clinical features if there is weakness at the subcortical cortex? What are some causes?
Equal brachio- crural weakness
Specific lacunar syndromes
No cortical or brainstem signs
Hemisensory loss
Causes
- Neurochemical: PD
- Structural atrophy: Huntington’s
- Normal Pressure Hydrocephalus
What are the clinical features if there is weakness at the brainstem ?
Crossed Signs:: Characterised by IPSILATERAL CN abnormality and CONTRALATERAL long tract abnormality (weakness and numbness)
Cerebellar signs
- Dysmetria, Dysdiadochokinesia
- Ataxia (Cerebellar, Ipsilateral, wide based gait, truncal ataxia as well)
- Nystagmus (multi-directional, does not correct on gaze fixation)
- Intention Tremor
- Staccato / Scanning Speech
- Hypotonia
Altered mentation
Cranial nerve palsies
Crossed sensory loss
Trigeminal distribution of sensory loss
What are the clinical features if there is weakness at the spinal cord? What are some causes?
Bilateral signs (LMN at level, UMN below lesion)
Sensory, motor and DTR levels
Normal mental state and cranial nerves
Sphincter dysfunction
Potential forms or sensory loss
- anterior: spinothalamic loss
- hemicord: hemiparasthesia
- posterior cord- dorsal column loss
- central cord- cape distribution spinothalamic loss
Causes: Cervical Myelopathy, Tabes Dorsalis
What are the clinical features if there is weakness at the anterior horn cell? What are some causes?
No sensory
Can have UMN/ LMN signs: as AHC is on the margin between UMN & LMN
UMN: ↑ muscle tone/spasticity + hyperreflexia, dyspraxia, dysarthria, dysphagia
LMN: weakness/atrophy, tongue fasciculations, nasal speech
Causes: Motor neuron disease (aka Amyotrophic Lateral Sclerosis - ALS), Polio
What are the clinical features if there is weakness at the roots? What are some causes?
- Diffuse LMN signs (myotomal weakness, more obvious in the LL since UL always overlaps)
- Dermatomal sensory loss- indistinct
- Radicular symptoms (eg: radicular pain – SHOOTING pain down the limb in a dermatomal distribution)
Causes: Intervertebral Disc Prolapse, Spine Spondylosis (arthritis of the spine, where there is narrowing of the intervertebral foramina), Cauda Equina Syndrome (L3-end)
What are the clinical features if there is weakness at the plexus? What are some causes?
Tends to affect an entire limb!
- Upper Limb: Brachial plexus (C5-T1)
- Lower Limb: Lumbosacral plexus (L2-S2)
Complex motor and sensory involvement
Causes: Erb-Duchenne palsy, Klumpke’s Palsy
What are the clinical features if there is weakness at the nerve (mononeuropathy)? What are some causes?
LMN motor and sensory following innervation pattern - median, ulnar, radial, common peroneal, sciatic
Usually Affects Distal > Proximal
Causes: Carpal Tunnel Syndrome, Cubital tunnel Syndrome, mononeuritis multiplex
What are the clinical features if there is weakness at the NMJ? What are some causes?
Fluctuating, fatiguable, recoverable: Hence weakness tend to improve in the morning (due to rest), worsening throughout the day
Affects Proximal > distal
No sensory loss
Causes: Myasthenia Gravis, Lambert Eaton Syndrome
What are the clinical features if there is weakness at the muscle? What are some causes?
- ocular, bulbar possible
- proximal > distal usually
- no sensory loss
- Symmetrical – as striated muscle loss tends to be global
- Muscle cramps and pain + Weakness, Progressive
Causes: Muscular Dystrophy, Rhabdomyolysis, AI (polymyositis), Endocrine (Hyper/Hypothyroid, Cushing’s), Metabolic (Hypo/HyperK)
What are the clinical features if there is weakness at the nerve (polyneuropathy)? What are some causes?
Distal and Symmetrical
Sensory +/- Motor Loss following glove and stocking pattern
Usually Affects Distal > Proximal
Causes: Diabetic neuropathy, GBS, Vitamin B12 Deficiency, Charcot Marie Tooth
What is the presentation of miller fisher syndrome?
A regional variant of Guillain–Barré syndrome
Characterized by cranial nerve involvement and the triad of ataxia, areflexia, and ophthalmoplegia
What is the presentation of guillain barre syndrome?
Most cases preceded by upper respiratory tract infections or diarrhoea 1-3 weeks before its onset, most commonly caused by Campylobacter jejuni.
Progressive, symmetric, ascending muscle weakness & hyporeflexia +/- paraesthesia (always test reflexes when suspecting GBS) in a glove and stocking pattern
MAY involve CN7 (facial / bulbar involvement)
MAY also involve autonomic dysfunction (arrhythmia, HTN, HypoTN, bowel/bladder dysfunction)
Why is the weakness in NMJ + muscle is proximal but the weakness in plexus + single nerve + polyneuropathy is distal? What is the exception to the rule?
The best explanation for the predominantly distal weakness in neuronal disease is that longer motor (also sensory) nerve fibers are more exposed and vulnerable to the many processes that damage nerves.
An exception to this rule is the diffuse polyneuropathy of Guillain-Barre syndrome (presumed to be an autoimmune process).
In this case weakness may begin in the proximal muscles and this is presumably because the primary damage to nerves is occurring quite proximally (near the nerve root level).
What is the presentation of Cauda Equina syndrome?
- Saddleback anaesthesia
- Acute retention of urine
- Sciatica-type pain on one side or both sides, although pain may be wholly absent
- Paraplegia of LL
- Ankle reflex absent
