29: Polyneuropathy

Question 1

Examples of small-fiber peripheral polyneuropathies?

Answer 1

DM, amyloidosis, toxins, drugs, Tangier, Fabry, AIDS, hypertriglyceridemia

Question 2

Asymmetry of neuropathy symptoms would imply what?

Answer 2

1. Mononeuropathy multiplex pattern
2. Superimposed radic or entrapment neuropathy
3. Variant of CIDP

Question 3

When is mononeuropathy multiplex seen?

Answer 3

Vasculitis (e.g. polyarteritis nodosa, Churg-Strauss, Wegener’s, SLE, RA, Sjogren, hepatitis);
DM;
Inflammatory demyelinating polyneuropathy (Lewis-Sumner variant);
Multiple entrapments;
Infection (HIV, Lyme);
Infiltration (sarcoid, lymphoma, leukemia)

Question 4

Example of hereditary demyelinating polyneuropathies?

Answer 4

CMT I, IV, CMTX;
Dejerine-Sottas (CMT III), Refsum disease;
HNPP, metachromatic leukodystrophy;
Krabbe, adrenoleukodystrophy;
Niemann-Pick; cerebrotendinous xanthomatosis

Question 5

Acquired demyelinating polyneuropathies?

Answer 5

AIDP, CIDP (HIV, MGUS, osteosclerotic myeloma, Waldenstrom);
MMN with conduction block;
diphtheria;
Toxic (amiodarone, arsenic, glue sniffing)

Question 6

What ratio could help detect underlying axonal polyneuropathy?

Answer 6

Sural/radial amplitude ratio (less than .21 may be the cutoff…)

Question 7

in axonal polyneuropathy, what does involvement of proximal muscles as opposed to distal muscles suggest?

Answer 7

Possible porphyria, or combo of both peripheral nerve and nerve root pathology

Question 8

One way to differentiate axonal and demyelinating slowing?

Answer 8

Could compare conduction velocities recording a distal and proximal muscles across the same segment of nerve (e.g. EDB vs. TA when stimulating fibular nerve)

Question 9

What clinical clues could suggest primary demyelination disorder?

Answer 9

1. Global areflexia
2. Hypertrophic nerves
3. Moderate-to-severe muscle weakness with relative preservation of muscle bulk
4. Motor symptoms and signs more so than sensory

Question 10

Possible causes of GBS?

Answer 10

Campylobacter, CMV, EBV, Zika, HIV;
vaccination, surgery, trauma,malignancy;
immune checkpoint inhibitors…

Question 11

Signs and symps of GBS?

Answer 11

Rapidly ascending paralysis;
distal paresthesias, hypo/areflexia, bifacial weakness, bulbar weakness; autonomic dysfunction

Question 12

What can porphyria cause?

Answer 12

A severe, acute axonal sensorimotor polyneuropathy

Question 13

Why is there sural sparing in AIDP?

Answer 13

Preferential early involvement of the smaller myelinated fibers in AIDP (sural sensory fibers larger and have more myelin than the median and ulnar sensory fibers)

Question 14

Best predictor of prognosis in AIDP?

Answer 14

Distal CMAP amplitude (if low, or < 20 % of LLN), this predicts poor outcome or prolonged course

Question 15

Inheritance pattern of the different sub-types of CMT?

Answer 15

CMT1 is dominant and demyelinating;
CMT2 is dominant and axonal;
CMT4 is recessive and demyelinating;
CMTX is X-linked and demyelinating
(DDRX)

Question 16

In CMT1, what muscles are affected first and what muscles are affected later?

Answer 16

Intrinsic foot and lower leg anterior compartment;
later distal thighs and intrinsic hand muscles

Question 17

What does pathology of peripheral nerve in patient with CMT show?

Answer 17

Segmental demyelinating and Schwann cell proliferation with onion-bulb formation

Question 18

What are average conduction velocities in CMTX vs. CMT1A vs. CMT1B

Answer 18

CMTX (25-38) > CMT1A (20-25)> CMT1B (15)

Question 19

What is HNPP also known as?

Answer 19

Tomaculous neuropathy (due to sausage resemblance)

Question 20

What ages are affected in CIDP? How does it come about? What muscles are affected? Symmetric or asymmetric?

Answer 20

Fifth and sixth decade;
Immune-mediated;
Proximal AND distal muscles;
Asymmetric

Question 21

CIDP can respond to what treatments?

Answer 21

Plasma exchange, IVIG, immunosuppressive therapy;
prednisone, azathioprine, mycophenolate, cyclophosphamide, cyclosporine;
rituximab if IgM Ab’s present;
surg or radiation therapy for osteosclerotic myeloma

Question 22

CIDP shows nerve conduction abnormalities that are often a/symmetric?

Answer 22

Asymmetric

Question 23

What is characteristic of anti-MAG CIDP? What are these polyneuropathies associated with?

Answer 23

Markedly prolonged distal motor latencies (distal myelinopathy);
IgM monoclonal protein

Question 24

What can be used to treat MMN?

Answer 24

IVIG;
cyclophosphamide or rituximab

Question 25

Where is the attack occurring with MMNCB?

Answer 25

Nodes of Ranvier and paranodal regions (autoimmune)

Question 26

What can be seen on NMUS with CMT? What about CIDP, LSS, and MMNCB?

Answer 26

Diffusely enlarged and symmetric nerves;
multifocal and asymmetrically enlarged nerves

Question 27

What is more likely to show nerve hypertrophy, CIDP or AIDP?

Answer 27

CIDP