Peripheral Nerve Pathology Flashcards
Where does the PNS start
Intervertebral foramen
Loss of somatosensation or viscerosensation (numbness)
Anesthesia
Altered/abnormal somatosenation (tingling)
Pareathesia
Alternation in the type of sensation experience (painful reaction to normal non-painful stimuli )
Allodynia
Pain sensation that occurs spontaneously without actual pain stimulus present, typically described as ‘burning’, shock-like’ etc
Affects dorsal (posterior) or ventral (anterior) roots
Radiculopathy
Etiology of local pathology
Traumatic, compression (by disc herniation or osteophyte, spinal stenosis (narrowing of spinal canal), tumors, access, viruses including varicella-zoster (shingles), cytomegalovirus
Etiology of systemic pathology
Irritates roots to causes abnormal firing and/or loss of normal firing pattern, including diabetes, infection, inflammation, and auto-immune disease
Radicular pain
Spontaneous, radiating, shock like, cutaneous and muscle
Presentation of radiculopathy
- radicular pain
- anesthesia
- paresis
- distribution (focal and segmental)
- temporal profile (acute, subacute, or insidious)
Distribution of radiculopathy
Focal and segmental, dermatomal, myotomal
Temporal profile of radiculopathy
Acute, subacute, or insidious depending on the cause
Highly variable
Posteriolateral herniation
Disc impinges on lateral portion of dorsal or ventral root or proximal spinal nerve
Far lateral herniation
Near the intervertebral foramen impinging on both dorsal and ventral root
Central herniations
Common in lumbar vertebrae, impinges on multiple roots (cauda equina)
Disc of herniation usually impinges on what
Root of adjacent level #
Local manipulation and radical are pain or paresthesia
Straight leg raises produces traction on roots. Unaffected leg with symptomatic leg down.
Induced pain is a sign of local mass compressing roots
Compression or irritation of descending roots. Same range of various causes as with radiculopathy at more rostral levels.
Cauda equina syndrome
Motor deficits of caudal equina syndrome
Depend on whihc root levels are affected (L1-S4)
Causes saddle anesthesia (S2-S5)
Infection via nerve terminals of DRG sensory neuron, retrograde transport to cell body
Herpes zoster
How does herpes zoster initiate pain
Viral proliferation irritates neuron, alters firing pattern, spontaneous pain
Cutaneous blisters in dermatome
What’s the difference between dermatome map and cutaneous nerve
Dermatome is related to the actual spinal nerve, cutaneous map is where the cutaneous sensory nerves innervate a certain area
Damage to cervical, brachial, or lumbosacral plexus
Plexopathy
Location of plexopathy
Damage to part of plexus- root, trunk, cords, major nerves near their proximal origins
Etiology of plexopathy
- Anesthesia
- Paresthesia
- Wide spread pain over multiple dermatomes
- paresis of a muscle group
- fasciculations may or may not
- Focal distribution and likely multi segmental
- acute, fluctuations depending on case
Temporal profile of plexopathy
Acute, fluctant depedning on the cause
Location of mononeuropathy
Distal to plexus or not derived from a plexus (median or ulnar)
One nerve affected
Mononeuropathy
Presentation of mononeuropathy
- anesthesia (cutaneous map)
- paresthesis (cutaneous map)
- wide spread cutaneous nerve territory
- paresis of a muscle group, multi segmental
- fasciculations may or may not present
Distribution of mononeuropathy
Territory of one nerve, isolated muscle paralysis
Temporal profile of mononeuropathy
Acute, fluctuatant depending on the cause
Multiple nerves affected in a region affected
Polyneuropathy
Location of polyneuropathy
May distal nerves, often selective impact on large diameter axons (fine/discriminative touch, motor function)
Etiology of polyneuropathy
Auto-immune, mutation, toxins (lead)
Presentation of polyneuropathy
- sensory and motor
- paresis of several distal muscles, usually bilaterally
Distribution of polyneiropathy
Symmetrical and diffuse, distal extremities
Temporal profile of polyneuropathy
Acute, subacute, or insidious depending on the cause
Examples of polyneuropathy
Guillaine-Barre (autoimmune), Charcot Marie tooth (hereidatary), diabetic polyneuropathy (DM)
Autoimmune attack myelin sheath or oligodendrocyte. Detected as slowing of nerve conduction velocity
Demyelinating
Neurogenerative, genetic mutation? Detected as reduction in amplitude of nerve conduction
Axonopathy
Neuronopathy (axonopathy): sensory
Degenerative of neuronal cell bodies of sensory neurons in DRG
Neuronopathy (axonopathy): motor
Motorneurons of spinal cord
Location of diabetic polyneuropathy (DM)
Damage large diameter axons innervating distal extremities
Distribution of diabetic polyneuropathy
Diffuse and symmetrical due to glucose fluctuation
Presentation of diabetic polyneuropathy (DM)
Stocking and glove pattern (lower leg, hands, feet)
Temporal profile of diabetic polyneuropathy (DM)
Insidious/chronic
Guillaine-Barre syndrome (polyneuropathy)
Acute inflammatory demyelinating polyneuropathy (AIDP)
Etiology of Guillane-Barre syndrome
Often emerges after an infection resolves
Location of Guillane-Barre syndrome
Motorneuron function in distal legs, than arms, then facial (lower motorneurons)
Distribution of Gulliane-Barre
Symmetrical and diffuse
Lower motor neurons
Presentation of guillane-barre
Motor weakness is more evident than sensory deficits
What is Charcot-Marie-tooth disease (polyneuropathy, axonopathy)
Genetic mutation causing degeneration of sensory and lower motor neurons
Distribution of Charcot Marie tooth disease
Diffuse and symmetrical
Presentation of Charcot Marie tooth disease
Flaccid weakness, impaired fine/discriminative touch and proprioceptive (sensory ataxia, lower motor neurons), normal pain and temperature
Location of Charcot Marie tooth disease
Preferentially impacts large diameter axons/fibers
Temporal profile of Charcot Marie tooth disease
Insidious/chronic, progressive
What kind of signs for neuropathies
Lower motor neuron signs
Distribution of deficits of neuropathies
Fits with nerve distribution territory
What is there an absence of in neuropathies
- spastic weakness and hyperreflexia
- spinal cord signs (long tract signs or level down signs)
- brainstem signs (CN signs )
- supratentorial signs (mental status, visual deficits)
Is stocking and glove level down
No
Neurological exam for peripheral nerve pathology and other disorders
Can narrow the localization of the problem; what general level of the CNS or PNS, what levels can be ruled out as the source of the problem?
Nerve conduction studies
Can measure nerve conduction velocity (testing for demyelinated nerves) or amplitude (testing for axonopathy).
What do you do to test for demyelinated nerves such as in MS?
Nerve conduction velocity
What do you do to test for axonopoathy
Nerve conduction amplitude
Stimulation electrode in muscle and recording of muscle response (motor unit potentials), measuring amplitude and whether firing pattern is continuous (normal recruitment of fibers) or intermittent (impaired muscle fiber recruitment)
Electromyopathy
Shows firing is continuous (normal) or increased (compensatory) but amplitude is reduced
Myopathic disease
Shows intermittent firing (impaired recruitment) but normal amplitude
Neuropathic disease
To detec auto immune forms of neuropathy
Antibody testing
To detect nerve or muscle disease
Genetic testing
To assess tissue and cellular signs of myopathy
Muscle biopsy
Nerve conduction studies
Measure distance and latency to compound motor action potential recorded from muscle, then calculate velocity (should be the same at all locations) also measure amplitude
Different amps
Axonopathy
Different velocity
Demyelination
How is the pattern different in NMJ than in neuropathy
NMJ disorders can:
- No sensory loss (rare in neuropathies)
- Some show fatiguable weakenss
- Some may improve with sustained motor effort
- DX techniques for NMJ vs neuropathies: electromyography
Myopathies vs neuropathies
- No sensroy loss in myopathies
- Diffuse weakness in myopathies vs focal/multifocal/diffuse neuropathies
- Diagnostic techniques techniques for myopathies: EMG, muscle biopsy, genetic testing
- Diagnostic techniques for neuropathies: nerve conduction, genetics, blood
What is there none of in neuropathies?
Sensory loss
What kind of weakness in neuropathies?
Diffuse weakness
Diagnostic techniques for myopathies
EMG, muscle biopsy, genetic testing
Diagnostic techniques for neuripathies
Nerve conduction, genetics, blood
