27 - Monoclonal Gammopathy of Undetermined Significance (MGUS) Flashcards

Question

What does the gait unsteadiness indicate?

Answer 1

Gait unsteadiness suggests proximal and/or distal muscle weakness or loss of position sense

Answer 2

Fatigue is associated with a variety of neurological, muscular, metabolic, and hematological disorders

Answer 3

First blood testing... - Fasting blood glucose and A1C, creatinine, TSH, and B12 are the only truly informative blood tests for neuropathy. - Consider a plasma electrophoresis in older men to rule out multiple myeloma Next... - NCV and EMG testing

Answer 4

- NCV and EMG (the two components of an NCS or Nerve Conduction Study) - Most accurate for diagnosing peripheral neuropathy

Answer 5

- NCV-distinguishes axonal from demyelinating disease - EMG-distinguishes nerve from muscular disease - Limitation-unreliable at diagnosing small fiber neuropathy; gold standard for diagnosing large fiber neuropathy

Answer 6

Large fiber neuropathies *** They are unreliable when trying to diagnose small fiber

Answer 7

- Diabetes is classically described as a small fiber disease - However, diabetic distal symmetric polyneuropathy has damage to both large and small fibers Diabetes Care suggests that “after 40 years of living with type 1 diabetes, nearly all patients have small-fiber sensory neuropathy and a majority also has large-fiber nerve dysfunction”

Answer 8

Painful or painless lower limb dysethesias are highly predictive of peripheral neuropathy: comparison of different diagnostic modalities 42 patients had NCS - 90% had signs of small fiber neuropathy - 50% had signs of large fiber neuropathy

Answer 9

Nerve biopsy - Sural nerve biopsy - Evaluates only a small segment of nerve and can miss the pathology - Difficult to evaluate presence of demyelination - Use if vasculitis, amyloid, sarcoid, or malignancy are suspected

Answer 10

Useful only for diagnosing small fiber neuropathy Sensitivity of 90% Specificity of 95% PPV of 95% NPV of 91% There is LITTLE evidence that diagnosing by skin biopsy alters treatment options (so is it worth it?)

Answer 11

- A 2-part screening instrument composed of a 15 item questionnaire and a physical examination composed of a general inspection of the feet, checking for ulcerations, reflexes, vibratory sensation, and SWM - Neuropathy is defined as 7 or more positive responses on the questionnaire or a score >2.0 on the examination

Answer 12

Is MNSI valid? - Sensitivity-95% - Specificity-80%

Answer 13

- Assesses and quantifies sensory function - Different systems measure the detection threshold of accurately calibrated sensory stimuli (Vibratory, thermal, or painful) - These stimuli are often chosen because they relate to distinct neuroanatomic pathways with discrete fiber populations - QST systems are separable into devices that generate specific physical vibratory or thermal stimuli and those that deliver electrical impulses at specific frequencies

Answer 14

- QST results should not be the sole criteria utilized to diagnose structural pathology - Abnormalities on QST must be interpreted in the context of a thorough neurologic examination and other appropriate testing such as the EMG, nerve biopsy, skin biopsy, or appropriate imaging studies***

Answer 15

- Sensitivity ranged from 41% to 93% and specificity ranged from 68% to 100%. - Because of the heterogenous nature of the studies, a meta-analysis could not be accomplished… - We do not recommend the sole use of monofilament testing to diagnose peripheral neuropathy ***

Answer 16

Semmes-Weinstein monofilament exam 25% of diabetics have a positive SWM test

Answer 17

- All results negative except IgM level elevated at 2.4 gm/dL - Further studies showed less than 10% plasma cells in bone marrow, no monoclonal protein in urine, no lytic bone lesions, anemia, hypercalcemia, or renal insufficiency

Answer 18

MGUS (monoclonal gammopathy of undetermined significance)

Answer 19

- A form of paraproteinemia [monoclonal gammopathy due to clonal proliferation of B-cells (plasma cells)] - Also includes multiple myeloma, Waldenstrom’s macroglobulinemia, lymphoma

Answer 20

- Affects 1% of population with 10% of these (0.1%) having a neuropathy - IgG is most common, but IgM most common when neuropathy is found

Answer 21

- Nerve tissue damaged by deposition of antibodies specific for a myelin or axonal component - IgM usually associated with antibodies to myelin-associated glycoprotein (MAG) found in the paranodal regions of Schwann cells resulting in demyelination and remyelination - Other autoantibodies to peripheral nerve antigens include anti-asialo GM1, anti-GD1a, anti-GD1b, anti-GM-1, anti-GM-2, anti-GQ 1b, anti-sulfatide

Answer 22

17-30% of patients with MGUS transform to a malignancy in 10 years (usually lymphoma)

Answer 23

Treatment: - Steroids - Cyclophosphamide - IV immunoglobulin - Plasma exchange - Rituximab

Answer 24

66% of diabetic patients have some variety of neuropathy (current studies suggest 50%) - Polyneuropathy-50% - Carpal tunnel-35% (symptomatic and asymptomatic) - Visceral autonomic neuropathy-6% - Other-9% Only 20% of diabetics with neuropathy had symptoms

Answer 25

10% This means that not all of your diabetics with neuropathy have the neuropathy because of the diabetes

Answer 26

The diabetic with neuropathy is only due to diabetes if there is coexisting retinopathy and nephropathy ********

Answer 27

10% of diabetics with neuropathy have an etiology other than diabetes NEED to know that it is NOT ALWAYS diabetes *****