Neurology 2 Flashcards
What is obstructive hydrocephalus?
In subarachnoid haemorrhage/meningitis/TB/mass in posterior fossa can obstruct the foramina of Magendie and Lushka, this results in a blocking of CSF (obstructive hydrocephalus).
What are the signs of cerebellar syndrome?
Signs: ataxia, nystagmus
Patient feels drunk
Deficit is on the side of the cerebellar lesion (unlike rest of the brain)
How is the cerebellum located in the brain?
Cerebellum is attached onto the brainstem onto the cerebellar peduncles.
Above the brainstem, it is associated with the thalamus (sensory relay to cortex) and the internal capsule (motor relay to cortex).
Below is the spinal cord.
What are the outcomes of berry aneurysms?
⅓ die immediately
⅓ die in the next 48 hours
⅓ survive
What are the neural structures associated with the brain stem?
Cranial nerves III-VII
Descending motor tracts (pyramidal tracts, corticospinal) - cross at the medulla
Ascending sensory tracts (medial lemnisci)
Reticular activation system - multiple clusters of grey matter nuclei which surround the aqueduct of sylvius. Will send connections to the hypothalamus. Keeps you alive - heart beating, breathing, sleep, consciousness.
Cerebellar peduncles
What is the pathway of the ascending sensory tract?
In two parts - early (lateral spinothalamic tracts) and advanced (posterior columns) evolutionarily.
Peripheral nerve has slow-conducting unmyelinated C fibres.
When they go into the spinal cord, they cross a level or two above the point of entry.
It ascends on the opposite side and reaches thalamus to relay.
Advanced part crosses at the sensory decussation and relays in the thalamus.
What is cavernous sinus syndrome?
CN3, 4, 5, 6 run through the wall of the cavernous sinus.
Disease in this area - cavernous sinus syndrome (facial numbness and abnormal eye movement +/- dilated pupil).
What is the clivus?
The clivus is a bony part of the cranium at the skull base, a shallow depression behind the dorsum sellæ that slopes obliquely backward. It forms a gradual sloping process at the anterior most portion of the basilar occipital bone at its junction with the sphenoid bone.
Give some ways damage to CNs can affect patients and how they can be rectified?
Non-functioning eye due to damage to CN3, 4, 6 - glasses with prisms/squint surgery
Corneal injury due to damage to CN5 - eye drops and lubricant, gold weight to help close the eyelid, lateral tarsorrhaphy (stitch the corner of the eye closed)
Smile due to damage to CN7 - cross-facial nerve graft
Swallow - NG tube, tracheostomy, percutaneous enteral gastrostomy (PEG)
Voice - vocal cord injection
What are the disorders affecting the brain stem?
Tumour (¼ of all brain tumours) - meningioma, schwannoma, astrocytoma, metastasis, hemangioblastoma, epidermoid
Inflammatory - MS
Metabolic - central pontine myelonecrosis (necrosis due to decreased Na)
Trauma
Spontaneous haemorrhage - brain arteriovenous malformation (AVM), aneurysm
Infarction - vertebral artery dissection
Infection - cerebellar abscess from ear
What are the key features of Multiple Sclerosis?
Inflammatory, demyelinating disease Specific to the CNS Commonest cause of chronic neurological disability in young adults Usually begins at age 20-40 Early course is relapsing/remitting Progressive disability over time
What are the different types of Multiple Sclerosis?
Relapsing/remitting: random attacks over a number of years (more frequent in the first 3/4 years), recovery varies between attacks, disabilities often accumulate with each successive attack.
Chronic progressive: slow, inexorable decline in neurological function from disease onset,
Benign: few relapses, little disability
What factors influence who gets Multiple Sclerosis?
Genetic disposition
Environmental triggers
Chance
What is the epidemiology of Multiple Sclerosis?
Increased prevalence in Australia and New Zealand
Less prevalence at the equator due to increased Vit D
More prevalent in caucausians
More prevalent in women and they tend to get it earlier
MS prevalence rate can be altered by a change in the environment
Age at migration is critical for risk retention (potential for developing MS may be assigned early in life)
Identical twin – about 25%
Non-identical twin – about 4%
Half-sibling – about 2% not dependent on whether they are still in the same household
What are the factors that contribute to the presentation of MS?
Chance Where you live (latitude) Race Age Diet Sanitation Socioeconomic status Multiple gene loci Climate Mutation
What is the pathophysiology of MS?
Exposure to virus, T lymphocytes become primed against it, they will travel in the bloodstream, cross the blood brain barrier and start a cascade of immune response which will result in damage to the myelin, the axon and the cells producing the myelin. Demyelination can recover but it’s the damage to the axon which causes the problems (no recovery). Can remyelinate – but the myelin is thinner, so if the axon is stressed the conduction is impaired (symptoms come back) – known as Uhthoff’sphenomenon
Mainly a white matter disease (but also grey). You see lesions around the ventricles.
What are the types of MS?
1 – macrophage mediated demyelination in brain and spinal cord
2 – antibody-mediated demyelination in brain and spinal cord
3 – distal oligodendrogliopathy and apoptosis
4 – primary oligodendroglia degeneration
Types 3 and 4 are more rare
What are the characteristics of an active lesion in MS?
Demyelination with breakdown products present
Variable oligodendrocyte loss
Hypercellular plaque due to infiltration of inflammatory cells
Perivenous inflammatory infiltrate
Extension BBB disruption
Older active plaques may have central gliosis
What are the characteristics of an inactive lesion in MS?
Demyelination with breakdown products absent Variable oligodendrocyte loss Hypocellular plaque Variable inflammatory infiltrate Moderate-to-minor BBB disruption Plaques gliosed
How is plaque distribution related to the symptoms of MS?
Cerebal hemispheres - large variety of symptoms
Spinal cord - weakness, paraplegia, spasticity, tingling, numbness, Lhermite’s sign, bladder and sexual dysfunction
Optic nerve - impaired vision, eye pain
Medulla and pons - dysarthria, double vision, vertigo, nystagmus
Cerebellar white matter - dysarthria, nystagmus, intention tremor, ataxia
What is Lhermitte’s sign?
Lhermitte’s sign - a sudden sensation resembling an electric shock that passes down the back of your neck and into your spine and may then radiate out into your arms and legs
What are the typical and atypical symptoms of MS?
Typical - optic neuritis (impaired vision and eye pain), spasticity and other pyramidal signs, sensory symptoms and signs, Lhermitte’s sign, nystagmus, double vision, vertigo, bladder and sexual dysfunction
Atypical - aphasia, hemianopia, extrapyramidal movement disturbance, severe muscle wasting, muscle fasciculation
What are the types of disease progression in MS?
- Relapsing/remitting: clearly defined disease relapses with full recovery or residual deficit
- Primary progressive: disease progression from onset with/without plateaus
- Secondary progressive: initial relapsing followed by progressive
- Progressive/relapsing: progressive from onset with clear acute relapses
What are the diagnostic criteria for MS?
Two or more CNS lesions disseminated in time and space
Exclusion of conditions giving a similar clinical picture
What will the CSF electrophoresis be like in a patient with MS?
IgG oligoclonal bands are present in the CSF of MS patients.
What are the common differential diagnoses for MS?
SLE Sjogren's syndrome Lyme disease Syphilis AIDS
What are the types of treatment for MS?
Treating relapses of MS symptoms (with steroid medicine)
Treating specific MS symptoms
Treatment to reduce the number of relapses (disease-modifying therapies)
How would you treat spasticity as a symptom of MS?
Mild to moderate: oral medications
Focal disabling: peripheral nerve blocks
Severe: reversible and irreversible invasive procedures
General rehabilitation: removal of trigger factors, physical treatments
What are the side-effects of Betaferon?
Generally well-tolerated but side effects are: Injection site reactions Flu-like symptoms Mild intermittent lymphopenia Mild to moderate rises in liver enzymes
How would you treat tremor as a symptom of MS?
Oral medications - beta blockers, low-dose barbituates, Gabapentin, Izonizid, Carbamazepine, Clonazepam
Orthotic devices - weighted wrist bands, computer-controlled mechanical damping devices
Thalamic surgery - stereotactic thalamotomy, thalamic electrostimulation
How would you treat sexual dysfunction as a symptom of MS?
General sexual counselling
Erectile dysfunction - papaverine or prostaglandin E1, penile prosthesis, oral yohimbine
Ejaculatory dysfunction - no specific treatment
For women, lubricating gels, topical local anasthetics, relief of other symptoms
What is the prognosis of MS?
5-10% clinically milder with no disability
30% develop significant disability within 20-25 years
Survival rate is linked to disability
Death is usually due to secondary complications (respiratory or renal)
Marburg variant can lead to coma or death within days
What are the bad prognosis indicators for MS?
Male gender Late age of onset High number of attacks Short inter-attack interval Early residual disability Early motor, cerebellar and sphincter symptoms
How would you manage MS?
Immunomodulatory therapy for acute repulses, frequent relapses, aggressive illness, progressive illness
Management of symptoms
Non-pharmacological treatments - physio, occupational health
How would you treat acute relapses of MS?
Oral or intravenous Methylprednisolone can hasten recovery of acute exacerbation
Plasma apheresis can be used if steroids are contraindicated or ineffective
What are the therapeutic strategies for treatment of MS?
Prevention of immuno-activation
Modifying lymphocyte trafficking
Lymphocytes depletion
Immune reconstruction
What are the differential diagnoses for epilepsy?
Parasomnia e.g. narcolepsy TIA Dystonia Cardiogenic syncope Postural syncope Hypoglycaemia Migraine Benign paroxysmal positional vertigo Cataplexy Hyperventilation Non-epileptic seizure
How to classify blackouts?
Primary disturbance of brain function - Could be epileptic seizures (including genetic generalised epilepsy, unclassifiable epilepsy, structural or metabolic epilepsy) or dissociative/non-epileptic seizures.
Secondary disturbance of brain function - related to the heart or low blood pressure.
What is an epileptic seizure?
Paroxysmal event in which changes of behaviour, sensation or cognitive processes are caused by excessive, hypersynchronous neuronal discharges in the brain.
Too much voltage - groups of brain cells are depolarising at the same time (added together). Spike in the EEG.
What are the clinical features of an epileptic seizure?
Duration: 30-120 seconds
‘Positive’ ictal symptoms (excessive of something - hearing/seeing/feeling/being touched when it’s not actually happening)
Postictal symptoms - weakness afterwards
Stereotypical seizures/syndromal seizure types
May occur from sleep - weakened by the state sleep (most vulnerable)
May be associated with brain dysfunction
Typical seizure phenomena - lateral tongue bite, deja vu (commonly the same each time for an individual patient).
What are the clinical features of a generalised secondary seizure?
Eye deviation to the right
Head deviation to the right
Right hand shaking
Gradual spread to both sides
TONIC: stiff, mouth open, eyes open, muscles are activated at the same time
CLONIC: individual spikes of activation of movement, big fast movements, relaxation and then more big fast movements. Amplitude grows but frequency decreases.
Staring into space, not really breathing properly.
What does it mean if a seizure is generalised?
both halves of the brain are doing the same thing (symmetrical). If it’s on both sides of the brain then both sides of the body are affected.
What are the clinical features of a partial seizure?
Different clinical features depending on which part of the brain is affected.. TEMPORAL Lip smacking Swallowing Slow movement of one hand Unconscious
FRONTAL
Awareness fully retained
No control of movements
What is syncope?
Paroxysmal event in which changes in behaviour, sensation and cognitive processes are caused by an insufficient blood or oxygen supplied to the brain.
What are the clinical features of syncope?
Situational
Typically from sitting or standing
Rarely from sleep
Presyncopal symptoms - seeing stars over the whole visual field, vision may go black, distorted sound, dizzy and light-headed
Duration 3-30 seconds
Recovery within 30 seconds
Cardiogenic syncope: less warning, history of heart disease
What is vasovagal syncope?
You faint because your body overreacts to certain triggers, such as the sight of blood or extreme emotional distress. It may also be called neurocardiogenic syncope. The vasovagal syncope trigger causes your heart rate and blood pressure to drop suddenly.
What is a Non-epileptic seizure (dissociative)?
Paroxysmal event in which changes in behaviour, sensation and cognitive function caused by mental processes associated with psychosocial distress.
People may not be able to recall what the distress was. May happen instead of a panic attack.
What are the clinical features of a Non-epileptic seizure (dissociative)?
Situational
Duration 1-20 minutes
Dramatic motor phenomena or prolonged atonia
Eyes closed
Ictal crying and speaking
Surprisingly rapid or slow postictal recovery
History of psychiatric illness, other somatoform disorder e.g. IBS, fibromyalgia
How would you differentiate between syncope and epilepsy?
Syncope - look for upright position, presyncopal symptoms, sweating, looking pale, nausea, rapid recovery
Epilepsy - look for tongue biting, head turning, muscle pain, prolonged loss of consciousness, cyanosis, postictal confusion
What are the common mistake when diagnosing epilepsy?
Incomplete history, lack of witness account
Misinterpretation of syncopal, myoclonic jerks
Misinterpretation of EEG-changes
What types of seizures do you get in structural/metabolic (focal) epilepsy?
Associated with focal brain abnormality, may start at any age.
Seizure types:
- Partial seizures without impairment of consciousness e.g. Jacksonian seizures, deja vu
- Partial seizures with impairment of consciousness e.g. psychomotor seizures
- Secondary generalised seizures
What causes structural/metabolic epilepsy?
Common cause: hippocampal sclerosis (mesial temporal seizure) caused by encephalitis or a prolonged febrile seizure.
Starts in one place and gradually spreads.
What’s the treatment for structural/metabolic epilepsy?
First-line treatment: Carbamazepine or Lamotrigine
What types of seizures do you get in genetic generalised epilepsy?
No associated brain abnormality, manifestation usually <30 years
Seizure types:
- Absence seizures e.g. childhood absence epilepsy, juvenile absence epilepsy
- Myoclonic seizures e.g. juvenile myoclonic epilepsy
- Primary generalised tonic clonic seizures e.g. grand mal on awakening
What is the treatment for genetic generalised epilepsy?
First-line treatment: Valproate or Lamotrigine
How can your pharmacologically treat epilepsy by targeting the pre-synaptic neurons?
PRE-SYNAPTIC EXCITABILITY
- Voltage-gated Na channel: Na increases excitability and drives action potentials. Inhibited by carbamazepine, lamotrigine, oxcarbazepine.
- Voltage-gated K channel: K efflux reduces neuronal excitability, channel increased by retigabine.
NEUROTRANSMITTER RELEASE
- Voltage-gated Ca channels: Ca influx drives neurotransmitter release. Channel inhibited by pregabalin and gabapentin.
- SV2A required for release of neurotransmitter from these vesicles. Inhibited by levetiracetem.
How can your pharmacologically treat epilepsy by targeting the post-synaptic neurons?
Target the GABA A receptor - reduces neuronal excitability. Increased activity by benzodiazepines, barbiturates, felbamate, topiramate.
Target GABA transaminase - degrades GABA, inhibited by vigabtrin (to elevate GABA levels)
Target the GABA transporter - removes GABA from the synapse, inhibited by tiagabine
How can you use anti-epileptic drugs?
Monotherapy: increase to lowest possible effective dose
Monotherapy: increase to fully effective/maximum tolerated dose
Consider alternative monotherapy/combination therapy
Consider epileptic surgery (electrical stimulation therapies)
Consider reduction to monotherapy in very refractory epilepsy
What to do if medical treatments for epilepsy fail?
Curative intent:
Resective surgery
Hemispherectomy
Palliative intent:
Tractotomy
Electrostimulation
How can vagal nerve stimulation be used as a treatment for epilepsy?
Stimulates 30 seconds every 5 minutes
When the heart rate goes up - given stimulation
Can reduce seizure frequency
What are the classical patterns of pathology related to different areas of the brain?
Cerebral hemisphere - unilateral dysfunction
Spinal cord - bilateral dysfunction in the legs
Cerebellum - loss of coordination
Brain stem - any that doesn’t fit the pattern
Peripheral nerves - mononeuropathies/polyneuropathies that don’t fit in dermatomes/myotomes
What questions do you need to be asking when a patient presents with neurological symptoms?
Where is the lesion? Single or multiple?
What is the likely pathology? E.g. inflammation, infection, neoplasm, vascular, neurodegenerative
Guided by the history and examination
What problems do different lesions cause in the optic tract?
Lesion at the optic chiasm you get bitemporal hemianopia - loss of temporal vision.
Lesion between optic chiasm and Meyer’s loop you get homonymous hemianopia - loss of one side in both eyes
Lesion at Meyer’s loop upper fibres you get inferior quadrantanopia - loss of bottom corner
Lesion at Meyer’s loop lower fibres you get superior quadrantanopia - loss of top corner
Lesion in the occipital pole (primary visual cortex) you get sparing of the macular
What is Nystagmus?
Nystagmus is a vision condition in which the eyes make repetitive, uncontrolled movements. These movements often result in reduced vision and depth perception and can affect balance and coordination. These involuntary eye movements can occur from side to side, up and down, or in a circular pattern.
What is Internuclear ophthalmoplegia?
Internuclear ophthalmoplegia (INO) is a disorder of conjugate lateral gaze in which the affected eye shows impairment of adduction. When an attempt is made to gaze contralaterally (relative to the affected eye), the affected eye adducts minimally, if at all. The contralateral eye abducts, however with nystagmus.
What can Asymmetrical nystagmus suggest?
Asymmetrical nystagmus may suggest internuclear ophthalmoplegia (may suggest MS)
What is surgical 3rd nerve palsy?
Surgical 3rd nerve refers to the space-occupying lesion that is pressing on the 3rd nerve.The parasympathetic fibres are on the outside so they will be pushed on - dilated pupil.
Can’t have a space-occupying lesion without pupillary involvement.
How can microvascular lesions cause nerve palsies?
Microvascular lesions tend to be found in elderly patients, almost always diabetic. Have 3, 4, 6th nerve palsies but are well. Treat the diabetes (occlusion of the microvasculature).
Most common cause of 3rd nerve palsy.
Can also have this with pupillary involvement.
What pathology can occur at the cavernous sinus?
Venous sinus thrombosis, metastases, carotid rupture, inflammatory syndromes can occur in the cavernous sinus.
Common area for pathology.
What is one and a half syndrome?
A rare weakness in eye movement affecting both eyes, in which one cannot move laterally at all, and the other can move only in outward direction. Characterized by “a conjugate horizontal gaze palsy in one direction and an internuclear ophthalmoplegia in the other”. Nystagmus is also present when the eye on the opposite side of the lesion is abducted.
What eye movements are not affected by one and a half syndrome?
Eye movements not affected include convergence, vertical CNIII movements, unilateral partial adduction.
What is Horner’s syndrome?
Horner’s syndrome - lesion in the sympathetic supply
Characterized by miosis (constriction of the pupil), ptosis (drooping of the upper eyelid), and anhidrosis (absence of sweating of the face).
What are the affects of lateral medullary syndrome?
Single lesion
Ipsilateral side: Horner’s syndrome Limb ataxia Loss of facial sensation of pain and temperature on face, reduced corneal reflex Dysarthria Dysphagia
Contralateral side:
Loss of pain and temperature sensation
If a patient presents with Horner’s syndrome and neck pain, what should you consider?
Consider vertebral artery or carotid artery dissection. Carotid dissection is more common.
What kinds of tract dysfunction does Brown-Sequard Syndrome cause?
At the level of the lesion: Ipsilateral Spinothalamic (localising sign)
Below the lesion:
Ipsilateral corticospinal tract dysfunction
Ipsilateral dorsal column dysfunction
Contralateral spinothalamic tract dysfunction
How can head injuries be classified?
TYPE OF INJURY
Non-missile (most common)
Missile head injury - penetration of skull or brain
DISTRIBUTION OF LESION
Focal (one particular area)
Diffuse brain lesions (across the brain)
TIME COURSE OF DAMAGE
Primary – due to immediate biophysical forces of trauma
Secondary – presenting some time after the traumatic event (physiologial responses, effects of hypoxia/ischaema, infection)
What are the different types of focal lesions?
Scalp - contusions (damage to tissue), lacerations (tear in the tissue)
Skull - Fracture
Meninges - Haemorrhage, Infection
Brain - Contusions, Lacerations, Haemorrhage, Infection
What are the different types of diffuse brain lesions?
Diffuse axonal injury
Diffuse vasucular injury
Hypoxia-ischaemia
Swelling
What are the features of a skull fracture?
Implies considerable force
↑ risk haematoma, infection & aerocele
Angled or pointed objects cause localized fractures that are often open or depressed
Flat surfaces cause linear fractures
Can extend to skull base (sometimes called contrecoup fractures)
What are the features of a Extradural haematoma?
~ 10% severe head injuries, ~15% fatal ones Usually associated with skull Occur slowly over hours Usually a lucid interval Causes death by - brain displacement - raised intracranial pressure - herniation
What are the features of a Subdural haematoma?
Usually due to tears in bridging veins that cross subdural space from superior surface of brain to midsagittal sinus
Dehydrated, elderly or demented patients are more vulnerable.
Can occur slowly (‘chronic’)
Usually surrounded by ‘membrane’ of granulation tissue
What causes a Traumatic subarachnoid haematoma?
Contusions/lacerations
Base of skull fracture (tear vessels)
Vertebral artery rupture/dissection
Intraventricular haemorrhage
What causes a cerebral/cerebellar haemorrhage?
Superficial: due to severe contusion
Deep: related to diffuse axonal injury
How does contact damage cause a focal brain damage?
At or just deep to the point of impact
How does acceleration/deceleration cause a focal brain damage?
Force to head causes differential movement of skull & brain. This can cause:
- Impact of inner surface of skull on underlying brain causes contusion
- Traction on bridging veins causes subdural haemorrhage
Differential movement of brain tissue which causes shearing, traction and compressive stresses and damages blood vessels and axons
How do contusions cause focal brain damage?
Superficial “bruises” of the brain
“Coup” at the site of impact
“Contre coup” – away from the site of impact
At first – haemorrhagic
Then become brown/orange and soft (days weeks)
Then indented or cavitated after months years
How do lacerations cause focal brain damage?
When contusion is sufficiently severe to tear the pia mater
What are the different types of axonal injury?
Axonal injury – a non specific term, can happen in a multitude of pathologies
Traumatic axonal injury – can be focal or widespread
Diffuse axonal injury
A clinicopathological syndrome of widespread axonal damage (inc brainstem)
But can be caused by a variety of processes
Diffuse traumatic axonal injury – over the brain due to trauma
Which areas are suceptable to diffuse traumatic axonal injury?
Corpus callosum
Midbrain
Pons
What are the different types of traumatic axonal injury?
Usually involves acceleration and deceleration of the head
Mild: recovery of consciousness ± long term, variable severity deficit
Severe: unconscious from impact & remain so or severe disability
What are the long-term effects of traumatic axonal injury?
Enlargement of the ventricles
Thinning of the corpus callosum
Curvy, linear lesions in the superior frontal lobe (gliding contusion)
Lose the myelination (pink colour)
What causes diffuse vascular injury?
Usually result in near immediate death
Multiple petechial haemorrhages throughout brain
What causes brain swelling?
Occurs in ~75% patients Leads to ↑ intra cranial pressure Caused by: - Congestive brain swelling Vasodilation and ↑ cerebral blood volume - Vasogenic oedema Extravasation of oedema fluid from damaged blood vessels - Cytotoxic oedema Increased water content of neurons and glia
What causes herniation?
Due to bleeding or swelling
What are some of the common sites of herniation?
Subfalcine herniation of the cingulate gyrus
Transtentorial herniation of medial temporal lobe
Transforaminal herniation of cerebellar tonsil
What is Hypoxia-ischaemia?
HI often causes infarction and hypoxic ischaemic damage
Likely in patients who have had
- Clinically evident hypoxia
- Hypotension with systolic BP<80mmHg for ≥15 min
- ↑ intracranial pressure
It can be widespread or confined to vulnerable regions
- Susceptible neurones
- Border zones between major cerebral territories
What areas are susceptible to Hypoxia-ischaemia?
Cortical laminar necrosis - pyramidal neurones which have long axons so high metabolic demand
Hippocampus cell populations
Purkinje cells in the cerebellum
What is chronic traumatic encephalopathy?
Seen following repetitive mild traumatic brain injury
Initially irritability, impulsivity, aggression, depression, memory loss
Then dementia, gait and speech problems, parkinsonism
Some have motor neurone disease-like symptoms
What is the pathology in chronic traumatic encephalopathy?
Atrophy: neocortex, hippocampus, diencephalon & mamillary bodies
Enlarged ventricles with fenustrated cavuum septum
Tau-positive neurofibrillary and astrocytic tangles in frontal and temporal cortex and limbic regions, especially around depths of sulci and limbic regions and blood vessels
What are the types of motor neuron disease?
Motor neurone disease (aka ALS) Heretidary spastic paraplegia Spinal muscular atrophy Kennedy’s disease Post-polio syndrome Motor neuropathies Hyperactivity disorders of the motor neurons e.g. stiff person syndrome
What is weakness?
AKA paresis
Impaired ability to move a body part in response to will
What is paralysis?
The ability to move a body part in response to will is completely lost
What is ataxia?
AKA incoordination
Willed movements are clumsy, ill-directioned or uncontrolled.
What are involuntary movements?
Spontaneous movement of a body part, independently of will.
What is Apraxia?
Disorder of consciously organised patterns of movement or impaired ability to recall acquired motor skills.
Where are the upper and lower motor neurons?
Upper motor neurons which have cell bodies sitting in the precentral gyrus and axons which travel down the brainstem and into the spinal cord via the corticospinal tract.
The lower motor neurons come from the motor nuclei in the brainstem and down the ventral horn of the spinal grey matter.
How to organise a movement?
Idea of a movement - association areas of cortex
Activation of the upper motor neurons in the precentral gyrus
Impulses travel to the lower motor neurons and their motor units via the corticospinal (pyramidal) tracts
Modulating activity from the cerebellum and the basal ganglia
Further modification of movement depending on sensory feedback
What is the final common pathway?
The pathway by which the CNS controls voluntary movement
Lower motor neurons have their cell bodies in the nuclei in the brainstem and spinal cord. Their axons join with other axons to form nerve roots and peripheral nerves.
It makes contact with muscle fibres at the neuromuscular junction.
What is the motor unit?
Basic functional unit of muscle activity. Lower motor neuron, axon and several supplied muscle fibres.
How is muscle tone controlled?
Stretch receptors in muscle (muscle spindles) are innervated by Y motor neurons.
When the muscle is stretched, afferent impulses from muscle spindles are sent to the spinal cord which cause a reflex partial contraction of the muscle.
Disease states e.g. spasticity and extrapyramidal rigidity alter muscle tone by altering the sensitivity of this reflex.
What are the potential sites of damage along the final common pathway?
Motor nuclei of cranial nerves Motor neurons in the spinal cord Spinal ventral roots Peripheral nerves Neuromuscular junction Muscle
What are the clinical features of lower motor neuron disease?
Muscle tone is normal or reduced (flaccid)
Muscle wasting e.g. in tongue, upper/lower limb, respiratory muscles
Fasciculation - visible spontaneous contraction of motor units
Reflexes depressed or absent
What are the pathological processes that will affect the motor neurons of the brainstem or spinal cord?
Motor neuron disease Spinal muscular atrophy Poliomyelitis Syringomyelia/syringobulbia Spinal cord/brainstem compression Vascular disease
What are the pathological processes that will affect the spinal roots?
Prolapsed intervertebral disc
Cervical or lumbar spondylosis
Tumours e.g. neurofibroma/ependymoma
Malignant infiltration
