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
What is pyramidal pattern of weakness?
Upper limb extensor weakness > flexor weakness
Lower limb flexor weakness > extensor weakness
Antigravity muscles are stronger! Due to Rubrospinal, Vestibulospinal, Tectospinal Tract > stronger than CS tract!
- UL: shoulder adducted to the chest wall, elbow and wrist flexed and fingers adducted together
- LL: When walking, the weak leg is extended, with the foot plantar flexed and internally rotated. All this makes the limb “too long”- so the only way to walk is to throw the foot outwards- a “circumductive gait”
How does posterior cord syndrome present?
Bilateral:
- vibration and proprioception
- preserved motor function
- bladder dysfunction
What are the causes of posterior cord syndrome?
- tabes dorsalis
- friedreich ataxia
- subacute combined degeneration
- AIDS myelopathy
- epidural metastases
- cervical spondylotic myelopathy
- multiple sclerosis
How does anterior cord syndrome present?
Bilateral
- Paraplegia (UMN)
- pain and temperature
- sphincter dysfunction (urinary retension)
What are the causes of anterior cord syndrome?
- anterior spinal artery infarction
- disc herniation
- radiation myelopathy
How does central cord syndrome present?
Mainly affects the Corticospinal Tract (paresis in UL > LL) + any decussating fibers (Spinothalamic) 🡪 spares dorsal column
Cape-like loss of pain / temperature sensation (or in fact may lead to pain instead of LOS)
What are the causes of central cord syndrome?
- Syringomyelia
- Intramedullary tumor
- Acute injury in cervical spondylotic myelopathy
How does brown sequard syndrome present?
Ipsilateral : voluntary motor (UMN), vibration and proprioception
Contralateral: pain and temperature 2-3 levels below the lesion
What are the causes of brown sequard syndrome?
- Knife or bullet injury
- MS
What is ataxia?
When a gait is referred to as ‘ataxic’ it means that an observer can’t consistently predict where the limb will land at the end of the protraction phase. Ataxia means without order. To say a gait is disordered or the animal is ataxic, may mean the patient is long-strided, limbs are too narrow or cross midline, limbs are too wide or circumduct, interfere or all of the above
What are the frontal cortical signs?
- CL gaze deviation (frontal eye fields)
- Behavioural changes, apathy, abulia (lack of motivation)
- Motor deficits
- Broca’s aphasia*
What are the parietal cortical dysfunction signs?
Sensory deficits
Constructional (drawing clock)/ dressing apraxia
Neglect/inattention
Gerstmann’s syndrome (supramarginal gyrus)
- AALF: tetrad of agraphia, acalculia, finger agnosia & left-right disorientation
Homonymous inferior quadrantonopia
What are the temporal cortical dysfunction signs?
Wernicke’s aphasia*
Homonymous superior quadrantonopia
What are the occipital cortical dysfunction signs?
Homonymous hemianopia, macular sparing
What are the lateral medullary syndrome signs?
- STT: pain/temperature (CL)
- SNS: Horner’s (IL)
- Spinocerebellar ataxia (IL)
- Spinal V nucleus: facial hemianaesthesia (IL)
- Swallowing/ speech (dysarthria): CN IX/X (IL)
- Sound/stability: CN VIII (IL)
What are the medial medullary syndrome signs?
Motor CNs (III, VI, XII)
Motor (CST – pyramidal decussation)
Medial lemniscus – proprioceptive/vibration loss
What are the signs of cerebellar dysfunction?
- Dysarthria (scanning & staccato)
- Nystagmus (central, may be mixed horizontal/vertical)
- Dysmetria/ dysdiadokokinesia
- Limb ataxia (veering to side of lesion; broad-based gait)
- Truncal ataxia
- Pendular reflexes (swinging excessively)
What are the clinical features of conus medullaris (tip of cord)?
EARLY: Sphincter loss (Bladder/bowel), Sexual Dysfunction & Sacral Sensory Changes
MINOR motor involvement
What are the clinical features of Cauda Equina
(spinal nerves in dura below L2/3))?
Unilateral/symmetrical
FIRST: Flaccid Lower Limb paralysis (LMN weakness, Hyporeflexia), Saddle Anaesthesia
THEN: Sphincter Involvement (Bladder/bowel), Sexual Dysfunction
What is the presentation of Tabes Dorsalis?
- Dorsal column degeneration
- Orthopedic pain (charcot joints)
- Reflexes decreased (deep tendon)
- Shooting pain
- Argyll- Robertson pupils
- Locomotor ataxia
- Impaired proprioception
- Syphyylis
What is the presentation of B12 deficiency?
Glove and stocking paraesthesia + UMN weakness (demyelination)
