SFPN: SINGLE FIBER PERIPHERAL NEUROPATHY

SFPN : Single Fiber Peripheral Neuropathy 
Peripheral neuropathy at its worst is SFPN
Involves small fibers
Narrow diameter : A theta thinly myelinated
Unmyelinated C fiber
Autonomic nervous system involvement
Cold + nociceptic
Preganglionic

Causes :
30% diabetes,
Other Metabolic: B12 def, Hypothyroidism, CKD : chr renal dis, hyperlipidemia,
50% idiopathic (SFPN & Burning mouth synd) 
Autoimmune
Inflammatory
Infection: HIV , Hepatitis C, Influenza Mitochondrial
Toxins:
👉🏿Antibiotics: Metronidazole, Nitrofurantoin, Linezolid(Zyvox)
👉🏿Antiretroviral
👉🏿 Chemo: Bortezomib
👉🏿Statin
👉🏿B6 toxicity
👉🏿B-12 def
👉🏿Alcohol
👉🏿Flecinide
👉🏿Thallium
👉🏿Lymes
Immune :
👉🏿 Monoclonal gammopathy
👉🏿Amyloidosis
👉🏿RA
👉🏿Celiac
👉🏿Sarcoidos
👉🏿 Sjögren's syndrom
👉🏿Rheumatoid arthritis
👉🏿Systemic lupus erythematosus
👉🏿Vasculitis
Inflammatory bowel disease
👉🏿Paraneoplastic
👉🏿Genetic / hereditary: 👉🏿Familial amyloid PN

S/S
Start in feet then hands : length dependent proximal progression, stocking & gloves
Stimulus dependent pain (bedsheets)
Burning, prickling, pruritic
Severe pin
Not many signs
PAIN : feet & hands: glove / stocking type, like frostbite, burning, shooting, prickling, pruritic numbness, temperature hypersensitivity, dry cracked shiny skin, allodynia, hyperesthesia.

👉🏿ANS (autonomic) : 
Postural hypotension
GI s/s
Impotence
Autonomic dysfunction

👉🏿Amyloid:
Lymphadenopathy
Organometallic
Thickened nerve, Congo red stain

👉🏿Tangiers : enlarged tonsils

👉🏿Fabrys: angiokeratoma, PN s/s, alpha galactosidase def. painful PN, early in young, late in older

🔺Possible: length dependent, allodynia, hyperalgesia, pin prick, thermal sensory loss,
🔺1+ normal NCV
🔺1+2+ altered nerve fiber density at ankle in some abn up to mid thigh, abn quantative sensory testing,
👉🏿 Skin biopsy: 3 mm punch biopsy heels in several weeks, fiber density w abn morphology,
👉🏿 Even sural n biopsy normal or mild abn
👉🏿Corneal confocal microscopy : abnormal nerve fibers in the cornea
🔴 ⬇️ Nerve fiber = ⬆️ SFN
🚦
Rx
Treat under lying causes
Complications of SFN : pain +ANS (autonomic nervous system)
Gabapentin/ Pregablin: binds to alpha 2 Theta1, Altered voltage gated gated calcium channels
TCA
SNRI
Duloxetine
Carbamazepine
Phenytoin
Topiramate
Baclofen
Lidocaine
Nonpharmacologic Rx: cool or warm soaks, soft socks, foot tents, TENS unit, PT / OT, Massage, Accupuncture, 
?  Vibra plate : not sure
+1
0
+1
0
+1
0
+1
0
+1
0

Leave a Comment