#MedTwitter #MedStudentTwitter #NeuroTwitter! This morning on @CPSolvers #VMR we discussed an approach to peripheral polyneuropathy so hereโs a #tweetorial to add to the #EndNeurophobia series
Link to whole series here:
@rabihmgeha @DxRxEdu @caseyalbin
Link to whole series here:
@rabihmgeha @DxRxEdu @caseyalbin
Peripheral neuropathy can be classified as:
Mononeuropathy: single nerve affected
Polyneuropathy: nerves affected throughout body symmetrically
Mononeuropathy multiplex: multiple individual nerves affected, asymmetric
Check out @DxRxEdu video!
clinicalproblemsolving.com
Mononeuropathy: single nerve affected
Polyneuropathy: nerves affected throughout body symmetrically
Mononeuropathy multiplex: multiple individual nerves affected, asymmetric
Check out @DxRxEdu video!
clinicalproblemsolving.com
MonoN and polyN are most common.
Mononeuropathy multiplex=rare
MonoN most commonly compressive or traumatic (ulnar neurop @ elbow, median neurop @ wrist, peroneal neurop @ fibular head)
Rarely: tumor (neurofibroma), infiltration (amyloid, neurolymphomatosis
Mononeuropathy multiplex=rare
MonoN most commonly compressive or traumatic (ulnar neurop @ elbow, median neurop @ wrist, peroneal neurop @ fibular head)
Rarely: tumor (neurofibroma), infiltration (amyloid, neurolymphomatosis
Mono multiplex: rare syndrome caused by relatively rarer diseases such as...Vasculitis, Hep C w/cryoglobulinemia, leprosy, HNPP (see schema)
PolyN = LONG Ddx including
Metabolic: diabetes, B12 deficiency, uremia
Toxic: Alcohol, chemotherapy, other meds
Inflammatory: GBS, CIDP
Infectious: HIV
Malignancy: paraprotein, paraneoplastic
Genetic: Charcot-Marie-Tooth, Fabry, Tangier
Metabolic: diabetes, B12 deficiency, uremia
Toxic: Alcohol, chemotherapy, other meds
Inflammatory: GBS, CIDP
Infectious: HIV
Malignancy: paraprotein, paraneoplastic
Genetic: Charcot-Marie-Tooth, Fabry, Tangier
Polyneuropathy should be suspected when
symmetric symptoms in extremities
- sensoryโnumbness, paresthesias, pain, imbalance +/-
- motorโweakness +/-
- autonomic dysfunction
Exam shows loss of sensation +/- weakness with diminished or absent reflexes
symmetric symptoms in extremities
- sensoryโnumbness, paresthesias, pain, imbalance +/-
- motorโweakness +/-
- autonomic dysfunction
Exam shows loss of sensation +/- weakness with diminished or absent reflexes
Polyneuropathy can be classified by:
- Modality/ies affected: sensory, motor, sensorimotor, autonomic
- Fiber type: large fibers vs small fibers (pain/temperature, autonomic)
- Pathophysiology: axonal vs demyelinating
- Modality/ies affected: sensory, motor, sensorimotor, autonomic
- Fiber type: large fibers vs small fibers (pain/temperature, autonomic)
- Pathophysiology: axonal vs demyelinating
So after localizing a patientโs syndrome as a polyneuropathy we can localize even further by classifying it based on modality affected, fiber type, and pathophysiology.
How? Symptoms and signs:
How? Symptoms and signs:
Small fiber N: +pain w/diminished pain sensation but preserved sensation in other modalities, motor, & reflexes (these functions are transmitted by large fibers)
DDx
Metabolic: DM
Toxic: ETOH
Inflammatory: Sjogren, sarcoid, celiac
Infection: HIV
Genetic: HSAN, Fabry, amyloid
DDx
Metabolic: DM
Toxic: ETOH
Inflammatory: Sjogren, sarcoid, celiac
Infection: HIV
Genetic: HSAN, Fabry, amyloid
Large fiber generally more numbness, tingling, imbalance, +/- weakness, absent reflexes
*Axonal v demyelinating distinguished by pattern/evolution of neuropathy symptoms/signs*
*Axonal v demyelinating distinguished by pattern/evolution of neuropathy symptoms/signs*
Axonal=LENGTH-DEPENDENT= longest fibers affected first: feet will be affected initially, hands not involved until LE symptoms/signs rise to level of mid-shin.
If dz process affects axons, longest ones affected most as most dependent on axonal function (compared to short ones)
If dz process affects axons, longest ones affected most as most dependent on axonal function (compared to short ones)
Demyelinating=NON-Length-dependent=UE &LE proximal and distal can be affected together @ onset, signs (e.g., reflex loss) more diffuse at presentation
If dz process affects myelin, all myelin affected = both short & long neurons
If dz process affects myelin, all myelin affected = both short & long neurons
*This distinction is key because helps w/DDX*
Many axonal neuropathies=toxic/metabolic
Many demyelinating=inflammatory
(Though there are many exceptions to this general principle: GBS can be either (AIDP vs AMAN/AMSAN), CMT can be either depending on mutation...)
Many axonal neuropathies=toxic/metabolic
Many demyelinating=inflammatory
(Though there are many exceptions to this general principle: GBS can be either (AIDP vs AMAN/AMSAN), CMT can be either depending on mutation...)
For chronic distal symmetric neuropathy evaluation per @AANMember guidelines, test for:
-DM: fasting glucose, glucose tolerance, or A1C
-B12 deficiency: B12 level +/- MMA
-Paraprotein: SPEP/IFE (rarer but canโt-miss cause of neuropathy)
n.neurology.org
-DM: fasting glucose, glucose tolerance, or A1C
-B12 deficiency: B12 level +/- MMA
-Paraprotein: SPEP/IFE (rarer but canโt-miss cause of neuropathy)
n.neurology.org
Paraprotein-related N complicated. See table here from amazon.com
Classic review @NEJM nejm.org
@ContinuumAAN review: @ElieNaddaf3
@mauermannmd journals.lww.com
Classic review @NEJM nejm.org
@ContinuumAAN review: @ElieNaddaf3
@mauermannmd journals.lww.com
If no etiology identified, expanded serologic workup can include:
- Rheumatologic testing
- HIV
- Heavy metals
- Paraneoplastic
- Genetic testing
- Rheumatologic testing
- HIV
- Heavy metals
- Paraneoplastic
- Genetic testing
This expanded work up guided by nerve conduction which can help determine if demyelinating (decreased velocity/increased distal latency) or axonal (decreased amplitude).
If concern for inflammatory cause (e.g., CIDP), LP to look for inflammation. Why would a PERIPHERAL condition show CSF inflammation? Because CIDP affects the roots which run through the CSF space. CIDP variants in table here from amazon.com
Still no answer? Consider nerve biopsy!
Acute peripheral neuropathy is less common, and DDx is smaller:
- GBS
- Acute heavy metal poisoning
- Porphyria
- (or perhaps itโs not neuropathy: consider botulism (NMJ d/o), acute poliomyelitis/flaccid paralysis (anterior horn cell d/o)
- GBS
- Acute heavy metal poisoning
- Porphyria
- (or perhaps itโs not neuropathy: consider botulism (NMJ d/o), acute poliomyelitis/flaccid paralysis (anterior horn cell d/o)
Big picture:
Conditions of peripheral nerve
- Mono v poly v mononeuropathy multiplex
- PolyN:
--small v large fiber?
--axonal (length-dependent) v demyelinating (non-length dependent)
Initial w/u A1c, B12, SPEP/IFE
Expanded NCS, Rheum, infxn, heavy metal, inflamm, genetic, LP
Conditions of peripheral nerve
- Mono v poly v mononeuropathy multiplex
- PolyN:
--small v large fiber?
--axonal (length-dependent) v demyelinating (non-length dependent)
Initial w/u A1c, B12, SPEP/IFE
Expanded NCS, Rheum, infxn, heavy metal, inflamm, genetic, LP
Like these tweetorials? Here's the whole list so far. What should I cover next?
Want to learn more #neurology in a clear and simple way? Check out my book FREE through AccessMedicine through your school digital library, or order here:
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Thoughts/additions/corrections? @caseyalbin @Tracey1milligan @CrystalYeoMDPhD @NMatch2023 @a_charidimou @MedTweetorials @CPSolvers @DxRxEdu @rabihmgeha @emeltzermd @zach_london @LyellJ @MariaMjaleman @gabifpucci
Here's our case discussion from this AM
@Rafameed @MariaMjaleman @CPSolvers @DxRxEdu @rabihmgeha
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@Rafameed @MariaMjaleman @CPSolvers @DxRxEdu @rabihmgeha
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