Lecture 10 - PNS Pathologies pt 1 Flashcards by Tempo Sabatier

what are the 3 subdivisions of PNS?

Somatic (voluntary) NS: cranial and spinal nerves that contain sensory and motor fibers
Autonomic (involuntary) NS: autonomic nerves
Enteric NS

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what is involved in somatic (voluntary) NS?

neurons from cutaneous and special sensory receptors to the CNS
motor neurons to skeletal muscles tissue

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what is involved in the autonomic (involuntary) NS?

sensory neurons from visceral organs to CNS

motor neurons to smooth and cardiac muscle and glands (ParaNS and SymNS)`

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what is involved in the enteric NS?

involuntary sensory and motor neurons controlling GI tract

- neurons function independently of ANS and CNS

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endoneurium surrounds each…

axon

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perineurium surrounds each…

fascicle

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epineurium surrounds each…

entire nerve

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what are 3 overarching SSx of disease of the PNS?

motor/somatic (LMN)
ANS/autonomic motor (pre and postganglionic fibers)
sensory/somatic AND autonomic (dorsal root ganglion, nerve root, peripheral nerve)

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where are cell bodies of lower motor neurons located?

anterior grey horn of spinal cord and cranial nerves of the brain stem

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where are axons of motor neurons located?

spinal and cranial nerves

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define ‘neuromuscular junctions’

muscle fibers innervated by motor nerve

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what are 5 main causes of peripheral nerve injuries?

hereditary
trauma
infections (herpes zoster)
toxins (tetanus; botulism)
metabolic (DM)

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how well does neurapraxia recover?

with segmental demylinisation the Schwann cells divide (mitosis) and new Schwann cells envelop demyelinised axons allowing for good recovery

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with axonotmesis, regeneration is possible if…

the never cell body remains viable

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new axons can sprout from the ….end of damaged axons

proximal

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what is required for successful functional regeneration of axons?

prox and distal end of CT must be aligned

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segmental demyelisation is caused by….and involves…

nerve compression/disease

loss of myelin in segments, but axon is intact

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what does peripheral nerve degeneration directly affect?

axons (axon degenerated distal to lesion)

what are 3 classifications of nerve injuries?

neurpraxia
axonotmesis
neurotmesis

does the muscle atrophy with neurapraxia?

no - axon stays intact

what causes axonotmesis?

prolonged nerve compression = damaged axon but CT intact (due to infarction and necrosis)

what can cause neurotmesis?

gunshot or stab wounds = muscle fibers rapidly atrophy (axon degenerates distal to injury)

when it comes to neurotmesis, what allows for re-mylinisation to occur?

axon establishes a distal connection

what are 4 neuropathy classifications?

mononeuropathy
polyneuropathy
radiculoneuropathy
polyradiculitis

define 'mononeuropathy'

focal neuropathy disorder involving a single peripheral nerve

what are main causes of mononeuropathy?

entrapment, compression, stretch injury, ischemia, infection, inflammation of nerve

define 'polyneuropathy'

neuropathy involving multiple peripheral nerves

what are 4 main causes of polyneuropathy and polyradiculitis?

DM (listed only for polyneuropathy) infections/toxins/drugs cancers nutritional deficiencies (vit B)

define 'radiculoneuropathy'

disease of spinal nerve roots (radix) and nerves

what causes radiculoneuropathy?

compression / irritation of the nerves as they exit the spine (herniation, osteophytes, thickened ligaments, tumors, DM)

define 'polyradiculitis'

inflammation of nerve roots

what are two major categories of SSx related to neuropathy?

loss of sensitivity following peripheral nerve distribution (dermatome when spinal nerve or root is involved) paresis or paralysis (mm distal to peripheral nerve - whole myotome)

what two things are affected first with paresthesia?

longest nerve and distal sensory deficits (hands and feet = tingling, pricking, burning)

what does 'glove and stocking distribution' relate to?

polyneuropathy of sensory nerves (dying back of fibers from distal to proximal)

what are 3 presentation of symptoms for distal muscle weakness/myopathy?

hypotonicity/flaccidity difficult to walk on heels or toes diminished or absent deep tendon reflexes

how does proximal muscle weakness present with myopathies?

muscle tenderness or cramping

what is the most common ANS motor disturbances presentations?

deficits in vascular control and sweating (hypotension and cardiac irregularities)

basic neurological assessment should be done in order from _______ of neurological function, down to ________ covering

highest level | the lowest

what are 5 categories covered in a basic neurological assessment?

1. mental status and speech 2. cranial nerve function (only if required for sensory or motor functions) 3. sensory function (focus on pain, touch, numbness) 4. motor function (tone, power - includes cerebellar function or abnormal muscle movements) 5. reflexes (deep tendon)

what nerves are being assessed with deep tendon reflex tests of the biceps tendon?

C5, C6

what nerves are being assessed with deep tendon reflex tests of the triceps tendon?

C7, C8

what nerves are being assessed with deep tendon reflex tests of the patellar tendon?

L2, L3, L4

what nerves are being assessed with deep tendon reflex tests of the achilles tendon?

S1, S2