Sunday, March 1, 2015

Ulnar neuropathy: Five new things

Campbell WW, Carroll C, Landau ME. Ulnar neuropathy at the elbow: five new things.  Neurology Clinical Practice  5:1 February , 2015 pp 35-41

1.  Authors note that the 10 cm rule was derived in 1972, in which error of velocity increased as distance decreased below 10 cm (Maynard FM and Stolow WC,  Experimental error in determination of nerve conduction velocity.  Arch Phys Med Rehabil 1972; 53: 362-372).  However, a 2003 study showed that with modern equipment, 6 cm is the new 10 cm and adequate error exists to measure velocity at 6 cm intervals (Landau ME, Diaz MI, Barner KC, Campbell WW.  Optimal distance for segmental nerve conduction studies revisited. Muscle Nerve 2003; 27: 367-369). 

Paradox is that measurements over greater distances decrease the experimental error but measurements over shorter distances increase the chance of detecting a lesion.  The type 2 error causes surgeons to use "clinical judgment" when deciding to operate.  Landau in another paper (Muscle Nerve 2003; 27: 570-574). determined the optimal distance to record velocities to minimize type I and type 2 erros is 4-6 cm.  Most ulnar lesions occur 3 cm proximal or distal to elbow.

2.  Cold elbow syndrome-- warmng the elbow can normalize some abnormalities.  (Landau ME, Barner KC, Murray ED, Campbell WW  Muscle Nerve 2005; 32: 815-817.

3.  Skinny elbow syndrome-- skinny patients are more likely to develop ulnar neuropathy.  However, they also are more likely to be overdiagnosed because rounder elbows are more likely to have a skin distance to nerve distance mismatch that overestimates NCV.  There is less margin for error and must avoid the temptation to overdiagnose.  Also must be aware of the possibility of overstimulation. 

4.  Short segment studies, called "inching" or per Kimura "centimetering," have been validated in the past ten years.  It should be considered as having additional diagnostic value in all cases of ulnar neuropathy (Visser LH, Beekman R, Franssen H.  Short segment nerve conduction studies in ulnar neuropathy at the elbow.  Muscle Nerve 2011; 43:627-635).

5.  High resolution sonography is emerging as a useful tool showing an increased cross sectinal area at the site of the compression.  However, it still is not considered definitive.

AANEM practice parameter in ulnar neuropathy at the elbow:

1.  The most important criterion is the presence of multiple internally consistent abnormalities.  Multiple abnormalities are more convincing than isolated abnormalities, which raises the possibility of "technical mishap."

    a.  Absolute motor NCV from across the elbow segment of < 50 m/s
    b.  An across the elbow segment of 10 m/s slower than the forearm segment
    c.  A decrease in the BE to AE CMAP peak amplitude of greater than 20 percent
    d.  A significant change in the CMPA potential at the AE site compared to the BE site

2.  If routine motor studies are inconclusive, the following may be used:

    a. NCS recorded from the FDI muscle
    b.  An inching or short segment study

3.  Needle examination should include the FDI, the most frequently abnormal muscle, and ulnar innervated forearm flexors.  Neither changes limited to the FDI nore sparing of the forearm flexors exclude an elbow lesion.  If ulanr innervated muscles are abnormal, the examination should be extended to include nonulnar C8/medial cord. lower trunk muscles to exclude brachial plexopathy and the cervical paraspinals to exclude radiculoapthy.

Thursday, November 13, 2014

Multifocal motor neuropathy: the diagnostic spectrum and response to treatment

Slee M, Selvan A, Donaghy M.  Neurology 2007; 69:1680-1687.
Authors look at 47 patients retrospectively and found that strict adherence to consensus criteria was a barrier to treatment.  Neither conduction block nor antibody status is a reliable predictor of treatment responsiveness.
Some of the pearls in the article:  Conduction block was present in 66%; GM1 antibody in a minority (25 %) and was not associated with conduction block. 27 % had lower limb onset, bu tin those patients, arm weakness typically developed subsequently.  Patients may have an acute or subacute onset with spontaneous resolution.  MMN can be PRECIPITATED by the use of steroids, and is usually not helped by steroids.  It "is evident from our study and others (Pakkiam AS, Perry GJ, Multifocal motor neuropathy without overt conduction block. Muscle Nerve 1998; 21: 243-245) that IVIG responsive  MMN occurs regularly without conduction block being demonstrated."  "A redefinition of conduction block which eliminates temporal dispersion as a restrictive factor and which helps predict IVIG responsiveness, (see Ghosh and Busby, JNNP 2005) categorized a further 15 % of our patients with conduction block."  "Our study suggests a decrement if IVIG responsiveness over time."  Using higher doses of 1.92 g/kg/6 weeks does better than Utrecht group of .54 g/kg /mo.  Disability self reports were more accurate than MRC scale scores with overall clinical change.
"Recognition of the clinical picture is the mainstay of diagnosis of MMN outside the researchg setting.  Weakness in nonwasted muscles and differential weakness across a common terminal motor nerve are the cardinal features.  Differential finger extension weakness is a frequent early manifestation likely reflecting vulnerabilities of the terminal branches of the posterior interosseous nerve." 
Blogger note-- this citation is extremely important for dealing with insurance companies to obtain approval for IVIG. 
Take away-- to take care of the patient, don't look at the test, be a doctor and a neurologist. 

Sunday, December 5, 2010

vincristine neuropathy nuggets and pearls

Verstappen CCP,Heimans Koeppen S, et al. JJ,  Dose-related vincristine-induced peripheral neuropathy with unexpected off-therapy worseningNeurology March 22, 2005 vol. 64 no. 6 1076-1077
Article described microtubule related neuropathy due to vincristine in 114 patients. 
1.  High dose group experienced more signs and symptoms than low dose group.
2.  Off therapy worsening signs and symptoms occurred in about 30 percent, mostly in the first month off. Most patients improved off therapy however.
3.  Paresthesias and numbness in both groups developed earlier in hands than feel and were more prominent in hands
4.  Paresthesias, numbness and pain occurred at more than 50 percent in both groups
5.  Resulting physical limitations include trouble buttoning clothes, climbing stairs, writing and walking
6. The dose intensity of VCR has changed considerably over the years. Studies 30 years ago describe dose intensities of 2 to 4 mg/week, frequently leading to a severe mixed sensorimotor peripheral neuropathy.Today, VCR is usually administered in a dose of ≤2 mg once every 1 to 4 weeks.
7.  Off therapy deterioration is also well described in cisplatin and paclitaxol related neuropathy.

Saturday, August 7, 2010

EMG is the practice of medicine Position statement of the American Academy of Neurology

What is the issue?

Needle EMG is a diagnostic neuromuscular exam that is used to identify potentially serious neuromuscular diseases ranging from carpal tunnel syndrome to Lou Gehrig's Disease. Despite the inherently diagnostic nature of these exams, non-physicians have been aggressively seeking the authority to perform these tests. Patients should know that only physicians should perform an intrusive, complex and intrinsically diagnostic test.

Why is it important?

To be properly performed, needle EMG requires physician training, including an in-depth knowledge of neuromuscular diseases. Also, EMG tests are dynamic and depend upon the observations of the examiner. A physician must be present to see what is happening and decide on the next step in the test, as there is no way to know after the fact whether the test was performed correctly. Misdiagnosis can mean delayed or inappropriate treatment (including surgery) and diminished quality of life.

What is the Academy's position?

The AAN Professional Association (Academy) opposes efforts by non-physicians to permit the performance of needle EMG by non-physicians.

What can you do to help?

The Academy has developed an advocacy toolkit (to the right) to help you advocate on this important issue.

North Carolina

Legislation in North Carolina that revises the North Carolina Physical Therapy Act includes language that states physical therapy can include "the performance of electrodiagnostic, electrophysiologic, and other specialized tests of neuromuscular function or physical capacities."

Thursday, April 1, 2010

Anti sulfatide neuropathies

clinical presentation is that of chronic axonal distal sensory neuropathy,symmetric, slowly progressive,  with pain in half and much less having any weakness. The frequency in idiopathic PN is only 0.7 %, but may be as high as 25 % in certain subgroups.  High titers are relatively specific for distal sensory neuropathy, whereas low titers can be seen in other conditons, including ITP, HIV, and autoimmune hepatitis.  Monoclonal gammopathies occur in half. 

GALOP (gait disorder, antibody, late age onset neuropathy) is a subgroup of antisulfatide neuropathy have monoclonal IgM  and antibodies to sulfatide and GALOP. 

anti GM1 antibodies pearls

1.  MMN with conduction block presents as asymmetric, painless, slowly progressive weakness especially in distal upper limbs. 
2.  Sensory sparing resembles ALS, however, UMN signs are not seen in MMN
3.   Conduction block outside of normal compression sites differentiates MMN and ALS.  Patients without conducton block occassionally respond to immunotherapy (Neurology 1997 first author JS Katz).
4. High titer IgM anti GM1 are seen in 50-60 percent of patients with MMN, but sensitivity is increased to 80-90 percent by complexing GM1 to secondary antigens co GM1 antibody test (Pestronk, Neurology 1997)
5.  In GBS, anti GM1 antibodies closely correlate with Campylobacter jejuni infection and sometimes correlate with worse neuropathy and outcome
6.  Other antigens coexpressed sometimes in GBS are GD1a, GD1b and GM2; some have argued GM2 correlates with CMV neuropathy but this is not univerally accepted.  GD1a is often seen in AMAN, the Chinese GBS variant (60 %) v. only 4 % of traditional GBS patients