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SA Neurology > Neuromuscular disorders > Flashcards

Neuromuscular disorders Flashcards

1
Q

Peripheral nerves

A

12 pairs of cranial nerves and 36 pairs of spinal nerves

Contain both motor and sensory axons

Limbs supplied by nerves from brachial or lumbosacral plexi

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2
Q

Neuromuscular juntion

A

Axon terminal, a synaptic cleft, and the endplate region of skeletal muscle

Junction is a transducer (electrical to chemical)

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3
Q

Clinical signs of muscle/nerve/synapse dysfunction

A

Generailsed weakness

Split into neuropathies, myopathies, and juctionopathies

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4
Q

Clinical signs of neuropathies

A

LMN disease

Usually severe impairment of motor function

Gait: Flaccid paresis or paralysis

Postural reaction: deficits

Spinal reflexes: Reduced/absent

Muscle tone: decreased to absent

Muscle mass: neurogenic muscle atrophy

Sensation: Decreased (hypoesthesia) to absent (anaesthesia). Paraesthesia, auto-mutilation

Cranial nerve deficits: V, VII, IX, X/XI, dysphagia, dysphonia, regurgitation due to megaoesophagus

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5
Q

Clinical signs of myopathies

A

Ventroflexion of the neck - especially in cats

Gait: generalised weakness, exercise intolerance, stiff and stilted

Postural reactions: usually normal

Spinal reflexes: usually normal

Muscle tone: usually normal

Muscle mass: muscle atrophy

Sensation: Usually unaltered, but can have muscle pain on palpation

Cranial nerve deficits: Usually unaltered but may be altered by involvement of masticatory muscles or impairment of swallowing

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6
Q

Neuromuscular diagnostic investigation (NM)

A

Haematology
Serum biochem (creatinine kinase and electrolytes)
Urinalysis (glucosuria, myoglobinuria)

Chest x-rays (megaoesophagus, aspiration pneumonia)

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7
Q

Peripheral nerve disorders causing generalised weakness

A

Idiopathic polyradiculoneuritis

Protozoal neuritis-myositis

Diabetes

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8
Q

Muscle diseases causing generalised weakness

A

Protozoal neuritis-myositis

Polymyositis

Hypokalaemia

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9
Q

Neuromuscular diseases causing generalised weakness

A

Myasthenia gravis

Botulism

Organophosphate and carbamates

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10
Q

Infectious causes of nerve/muscle ‘generalised weakness’

A

Protozoal polyradiculoneuritis-myositis

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11
Q

Inflammatory causes of nerve generalised weakness

A

Idiopathic polyradiculoneuritis

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12
Q

Inflammatory causes of muscle generalised weakness

A

Idiopathic polymyositis

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13
Q

Inflammatory causes of NM junction generalised weakness

A

Myasthenia gravis

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14
Q

Indiopathic causes of muscle generalised weakness

A

Exercise induced rhabdomyolysis

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15
Q

Toxic causes of nerve generalised weakness

A

Vincristine

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16
Q

Toxic causes of Muscle generalised weakness

A

Toxic rhabdomyolysis

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17
Q

Toxic causes of muscle generalised weakness

A

Botulism, organophosphates/carbamates, aminoglycosides

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18
Q

Metabolic causes of nerve generalised weakness

A

Diabetes mellitus
Hypothyroidism

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19
Q

Metabolic causes of muscle generalised weakness

A

Cushing’s myopathy
Hypothyroidism
Hypoadrenocorticism
Hypokalaemic myopathy

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20
Q

Neoplastic causes of nerve generalised weakness

A

Paraneoplastic: insulinoma

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21
Q

Neoplastic causes of muscle generalised weakness

A

Paraneoplastic: lymphoma

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22
Q

Neoplastic causes of NM junciton generalised weakness

A

Paraneoplastic

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23
Q

Degenerative causes of nerve generalised weakness

A

Inherited neuropathies

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24
Q

Degenerative causes of muscle generalised weakness

A

Inherited myopathies

25
Q

Degenerative causes of NM junction generalised weakness

A

Myasthenia congenita

26
Q

Pathogenesis of idiopathic polyradiculoneuritis

A

Signs caused by immunemediated attach to the axons and myelin sheaths at level of ventral nerve roots

27
Q

Epidemiology of idiopathic polyradiculoneuritis

A

Most common peripheral neuropathy

28
Q

Clinical signs of of idiopathic polyradiculoneuritis

A

Start acutely in the pelvic limbs

Rapidly progress to LMN tetraparesis or tetraplegia

29
Q

DIfferential diagnosis of idiopathic polyradiculoneuritis

A

Looks very similar to Botulism, but in botulism the cranial nerve deficits are more prominent

30
Q

Diagnosis of idiopathic polyradiculoneuritis

A

Electromyography reveals denervation potentials

Nerve conduction velocities are reduced

CSF can show an increase in mononuclear cells.

Bloods (serology neospora exclusion)

31
Q

Prognosis of idiopathic polyradiculoneuritis

A

Outcome is good - recover over a period of 3-6 weeks

32
Q

Treatment of idiopathic polyradiculoneuritis

A

Supportive care and rehabilitation

Corticosteroid administration is not beneficial

Monitor pulmonary function

33
Q

Pathogenesis of myasthenia gravis

A

Failure of NM transmission due to reduction in number of functional nicotinic actylcholine receptors

An immune-mediated disease caused by an over-production of antibodies directed against acetylcholine receptors

34
Q

Epidemiology of myasthenia gravis

A

Relatively common in dogs
Relative rare in cats

Usually occurs spontaneously

Can be associated with thymoma or other neoplastic/immunemediated diseases

35
Q

Clinical signs of myasthenia gravis

A

Focal: facial, oesophageal, laryngeal, and pharyngeal weakness, resulting in regurgitation and dysphagia

Generalised: exercise intolerance, regurgitation, stiff gait with short strides

Acute fulminant form of generalised: very rapid onset or paralysis and regurgitation - rare

36
Q

Diagnosis of myasthenia gravis

A

Resolution of muscle weakness following IV injection of edrophonium chloride

Repetitive nerve stimulation- decremention of the action potential

Serum sample: ACh antibodies

Chest x-ray for cranial mediastinal mass

37
Q

Prognosis of myasthenia gravis

A

Good
Clinical remission is 6 months

Guarded if persistent megaoesophagus

38
Q

Treatment of myasthenia gravis

A

ACh inhibitors
- pyridostygmine
- neostigmine in case of severe regurgitation

Immunosuppressive therapy
- steroids
- controversial

39
Q

Neuromuscular diseases causing ‘focal weakness’

A

Aortic thromboembolism
Masticatory myositis (muscle)
Brachial plexus avulsion
Sciatic nerve injury
Nerve sheath tumour

40
Q

Pathogenesis of aortic thrombosis

A

Obstruction of aortic or iliac arteries

Common underlying cause: hypertrophic cardiomyopathy

Restriction of blood flow by embolus causes ischaemia to the sciatic nerve and muscles of the pelvic limbs

41
Q

Epidemiology of aortic thrombosis

A

Most commonly seen in cats

42
Q

Clinical signs of aortic thrombosis

A

Acute onset of pelvic limb paresis/plegia,
loss of pelvic limb nociception distally,
Weak or absent femoral pulse
Cold limbs
Cyanotic nail beds
Very painful
Signs of heart failure may be present

43
Q

Diagnosis of aortic thrombosis

A

Based on clinical signs

Marked elevated serum CK present in first 1-2 days

Chest x-rays and echocardiography - evidence of cardiac disease

44
Q

Prognosis of aortic thrombosis

A

Long term prognosis poor - association with heart disease

Worth treating if pain can be controlled

45
Q

Treatment of aortic thrombosis

A

Management of cardiac disease

Low dose aspirin to prevent further blood clots - controversial

Pain relief is mandatory

46
Q

Pathogenesis of (malignant) peripheral nerve sheath tumours

A

Aggressive biological behaviour

Most commonly affects the caudal cervical (C6-C8) and cranial thoracic (T1-T2)

Spread slowly

May invade vertebral canal causing spinal cord compression

Highly invasive locally but rarely metastasize

47
Q

Epidemiology of (malignant) peripheral nerve sheath tumours

A

Brachial plexus tumours are seen in adult, older dogs.

Cats will rather have a lymphoma of the brachial plexi

48
Q

Clinical signs of (malignant) peripheral nerve sheath tumours

A

Slowly progressive thoracic lameness, paresis and muscle atrophy

Pain on palpation of the axillary region

Axillary mass may be palpable

Ipsilateral partial or complete Horner’s syndrome, and ipsilateral absent cutaneous trunci reflex

49
Q

Diagnosis of (malignant) peripheral nerve sheath tumours

A

Diagnosis by exclusion of orthopaedic disease and radiographs of thoracic limbs.

Electromyogram shows abnormal and spotnaeous muscle activity

Chest x-rays and abdominal ultrasound performed to metastatic disease

MRI of brachial plexus or peripheral nerves can visualise the nerve root tumour

50
Q

Prognosis of (malignant) peripheral nerve sheath tumours

A

Poor with high recurrence rate after surgery (amputation)

51
Q

Treatment of (malignant) peripheral nerve sheath tumours

A

Local excision is rarely possible; usually leg amputation with or without spinal decompression is needed

52
Q

Pathogenesis of brachial plexus trauma

A

Usually caused by a road traffic accident or fall from height - abduction and caudal displacement of thoracic limbs

Site of avulsion is usually intradural

53
Q

Epidemiology of (malignant) peripheral nerve sheath tumours

A

Most common cause of acute thoracic limb monoparesis/plegia in small animals

54
Q

Clinical signs of (malignant) peripheral nerve sheath tumours

A

Peracute onset of monoparesis/plegia following traumatic incident

Avulsions

Ipsilateral partial Horner’s syndrome and/or loss of cutaneous trunci reflex

55
Q

Three types of avulsion

A

Cranial avulsions (C6-7) - rare, few clinical signs

Caudal (C8-T2) or Complete (C6-T2)
- more common
- more severe clinical signs
- paralysis of brachial triceps

56
Q

Diagnosis of (malignant) peripheral nerve sheath tumours

A

Acute history of a traumatic incident
Electromyogram allows detection of spontaneous electrical activity in denervated muscles 7-10 days after injury

57
Q

Prognosis of (malignant) peripheral nerve sheath tumours

A

Most cats still have pain sensation on presentation, compared to dogs

Prognosis is good if deep pain sensation is present

If deep pain absent, prognosis will depend on the severity of the axonal injury

58
Q

Treatment of (malignant) peripheral nerve sheath tumours

A

No routinely effective treatment

Amputation of limb may be needed but wait 2-3 months to see if recovery occurs

SA Neurology (11 decks)

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