Muscle weakness [Ix and Mx] Flashcards
Where are the ascending tracts on the spinal cord? Give examples of ascending tracts.
Look slides
Where are the descending tracts of the spinal cords?
Look slides
Main way of subgrouping the descending tracts
Pyramidal vs extrapyramidal tracts
What is the origin and function of the pyramidal tracts?
Origin: cerebral cortex
Function: responsible for the voluntary control of the musculature of the body and face
What is the origin and function of the extrapyramidal tracts?
Origin: brain stem
Function: responsible for the involuntary and automatic control of all musculature such as muscle tone, balance, posture, and locomotion
Where do the pyramidal tracts derive their name from?
The medullary pyramids of the medulla oblongata which they pass through
Functionally, how can the pyramidal tracts be subdivided into?
Corticospinal tracts: lateral and anterior
Corticobulbar tracts
Which part of the corticospinal tract decussates at the medulla?
The lateral corticospinal tract and terminates in the ventral horn [at all segmental levels]
What is the route of the anterior corticospinal tract?
Cerebral cortex -> internal capsule -> medulla [remains ipsilateral] -> decussates/terminates in the cervical and upper thoracic segmental levels
Where do the extrapyramidal tracts originate from?
Brainstem
What do the extrapyramidal tracts carry?
Motor fibres to the spinal cord
How many extrapyramidal tracts are there in total?
4 tracts:
- vestibulospinal [do not decussate, ipsilateral innervation]
- reitculospinal [also ipsilateral]
- rubrospinal [decussate, provide contralateral innervation]
- tectospinal [decussate, provide contralateral innervation]
What are the two parts to the PNS?
- somatic nervous sytem [incl. cranial nerves]
- autonomic nervous system
Why is the PNS more vulnerable to damage than the CNS?
PNS not protected by the vertebral column and skull, or by the blood-brain barrier which can leave it exposed to toxins and mechanical injuries
Which cranial nerve is NOT part of the PNS?
optic nerve [II]
How many pairs of spinal nerves are there in the somatic nervous system? Divide into bodily areas
31 pairs:
- cervical: 8
- thoracic: 12
- lumbar: 5
- sacral: 5
- coccygeal: 1
Compare an UMN to a LMN
look up
What is in a muscle weakness history?
Onset [instant/gradual], distribution [proximal/distal, symmetrical/asymmetrical, mono or local process/poly or diffuse, cranial involvement e.g. bulbar or facial or ophthalmoplegia], variability [fatigueability/relapse remissions], additoonal features [sensory Sx like tingling or pins or loss sensation], context [recent illness/PMH/FH/drugs/alcohol]
Motor system examination for a UMN lesion
Bulk - normal Tone - increased Strength - decreased Fasciculations - absent Reflexes - increased
Motor system examination for a LMN lesion
Bulk - reduced [wasting Tone - normal or decreased Strength - decreased Fasciculations - may be present Reflexes - decreased or absent
Go through the 5 parts to the grading of the muscle power system
MRC look up
List example causes of weakness
Neuropathies: - peripheral neuropathy - GBS - myasthenia gravis - MND Myopathy
What are the three ways of classifying damage to peripheral nerves?
Polyneuropathy [peripheral neuropathy]
Mononeuropathy multiplex [mononeuritis multiplex; at least two nerves]
Mononeuropathy: one single nerve
What does peripheral neuropathy describe? Progression, where does it start, and is it sensory or motor?
Essentially, describes disease affecting the peripheral nerves
usually, chronic and slowly progressive
Starts in the legs and longer nerves
Sensory or motor or both
Examples of peripheral neuropathies with predominantly motor loss
- Guillain-Barre Syndrome [GBS]
- Chronic Inflammatory demyelinating polyneuropathy [CIDP [i.e. chronic version of GBS]]
- Hereditary sensorimotor neuropathies [HSMN] e.g. Charcot-Marie-Tooth Disease
- Diptheria
- Porphyria
Examples of diseases with predominantly sensory loss
- Deficiency states e.g. B12/folate
- Diabetes
- Alcohol/toxins/drugs
- Metabolic abnormalities e.g. uraemia
- Leprosy
- Amyloidosis
Is GBS motor or sensory?
Motor
Diabetic neuropathy motor or snesory?
Sensory I think
CMT motor or sensory?
Look up
Define mononeuritis multiplex
Painful, asymmetrical sensory and motor neuropathy
How does Mononeuritis multiplex present, how is it mediated and what are the causes?
Presentation: subacute
Inflammatory/immune mediated
Causes: vasculitides e.g. Churg Strauss, connective tissue disorders
What is a mononeuropathy? Common location of presentation. Give 4 examples
Individual nerve deficits in isolation
Upper limb nerves most commonly affected at compression points
Median nerve entrapment at the wrist most common [Carpal Tunnel Syndrome]
Ulnar nerve at elbow common also
Radial nerve in axilla common
Common peroneal nerve in leg most common
Describe Carpal Tunnel syndrome
look up. Essentially, I think flexor reticunalum.
Neuropathy investigations
History and examination:
- neuropathy screen
- vasculitic screen
- EMG/NCS
- CSF study
- imaging/nerve biopsy
What does a neuropathy screen involve?
FBC, ESR U&E, glucose, TFT, CRP, serum electrophoresis B12 folate anti-gliadin TPHA, HIV
What does a vasculitic screen involve?
FBC, ESR
U+E, Cr, CRp, ANA, ANCA, anti-dsDNA, RhF, complement cryoglobulins
Neuropathy treatment
20% idiopathic with no Tx
- neuropathic analgesic [gabapentin, pregabalin, amitrptyline]
Treat/remove underlying cause e.g. DM/B12 deficiency
Inflammatory neuropathy [e.g. CIDP - chronic version of GBS]
- prednisolone with steroid sparing agents e.g. azathioprine
Vasculitis neuropathy [e.g. with Wegners]
- prednisolone with immunosupressaant e.g. cyclophosphamide
Describe the mechanism of Guillain-Barre syndrome
slides
What type of disease is GBS?
Autoimmune response causing demyelination
Common trigger for GBS?
Post-infectious; resp or GI [e.g. campylobacter]
progression of GBS
Subacute [less than 6w], ascending paralysis/numbness/areflexia
What would NCS show?
Demyelinating
What would LP show?
Raised CSF protein
How to treat GBS
Treat with IVIg or plasmapharesis, support, monitor FVX, ITU review
Recovery may take weeks to years
Eyes for people with myasthenia gravis
look up
Which NT does myasthenia gravis affect?
Autoimmune disorder that effects antibodies against nicotinic acetylcholine receptors
How treatable is it, and what is also commonly associated with myasthenia gravis?
Common disease itsefl, potentially fatal but treatable
Thymus dysfunction is common
-hyperplasia
- thymoma
Dsecribe the pathophysiology of myasthenia gravis
slides
Which muscles does MG effect?
Generalised:
- fatigueable weakness: proximal limbs, neck and face [head drop, ptosis], extraocular [complex diplopia], bulbar [speech, swallow] particularly elderly
Ocular [10-25%]
At risk of other autoimmune diseases [thyroid, PA etc.]
MG investigations
Tensilon test [allow accumulation of Ach in the NMJ]
AChR antibodies
EMG: looks at NMJ
CT thorax
MG treatment
Acetylcholine esterase inhibitors [pyridostigmine] - symptomatic
Immunosuppresants: steroids [start slowly], azathioprine/MTX/mycophenolate
Thymoectomy
What is a myasthenic crisis?
Severe weakness including respiratory muscles
High risk of death
Cause of a myasthenic crisis
Infection, natural disease cycle, under dosing or overdosing of medication
Action taken during a myasthenic crisis
- Take change in myasthenic condition seriously
- urgent review by nuerologist
- think about breathing and monitor
- anaesthetic review
What is MND?
Degeneration of motor neurones in the motor cortex and anterior horns of the spinal cord
What type of signs does MND present with
UMN and LMN signs
Investigations done in MND
LP, NCS/EMG and MRI [to r/o other conditions]
How is MND Dx?
Mainly a clinical Dx
Clinical signs of MND
No sensory, visual or B/B involvement
Asymmetric weakness
Bulbar or limb onset
Survival usually 2-5 years
What are the four common muscle disorders?
Steroid myopathy
Statin myopathy
Metabolic and endocrine myopathies
Myotonic dystrophy
what are some uncommon muscular disorders?
Most muscular dystrophies:
- Duchenne, Becker, Facioscapulohumeral muscular dystrophy [FSHD]
Inflammtory muscle disease:
- polymyositis, dermatomyositis
Mitochondrial disorders
Which muscles commonly and noticeably affected in muscle disorders? Other muscles less commonly affected?
Stairs, chairs and hair muscles
Facial weakness occurs in some e.g. facioscapulohumeral dystrophy
Neck weakness can occur
Contractures can occur
Scoliosis is oftena feature esp. in Duchenne
Eye movement disroders rare [seen mitochondrial]
Which muscle condition scioliosis common feature?
Duchenne
Eye movement disorders are common or rare muscular disorders?
Rare [seen in mitochondrial]
Muscle investigations done
CK, EMG, ESR/CRP
+/- genetics [DMD/Becker]
+/- biopsy
Muscle disorders Tx
Remove causal agent Supportive - OT [aids adaptions] - physio [prevent contracture] - back - renal - diet Immunosuppres if inflammatory
Type of weakness comparin gnerve disease to muscle disease
nerve disease - distal weakness
muscle disease - proximal weakness