Peripheral Neuropathies - Neuro

Question 1

patient will complain of

Answer 1

• weakness (dropping things, can’t walk, off balance, difficulty with stairs or getting out of a chair, difficulty with ADLs…)
• sensory changes (numb, tingling, off balance…)
• pain (burning, weird discomfort…)
• autonomic symptoms (hot/cold changes, skin color changes, swelling changes…)

ask pt: are you weak? do you have numbness? do you have pain, especially a burning pain? have you noticed significant changes in your skin temperature or color? do your feet and/or hands swell?

Question 2

APPROACH: 8 questions to answer

Answer 2

• motor, sensory, autonomic or combo: if sensory, is it small fiber (pain and temp) vs. large fiber (vibrio and proprio) disease
• distal vs. proximal
• focal/asymmetric vs. symmetric
• any UMN involvement
• acute 2m
• family h/o PN
• assoc medical condition (cancer, DM, connective tissue dz, infection, toxic medications, toxins, drugs)

Question 3

SIGNS AND SYMPTOMS

Answer 3

weakness with sensory changes

• is it distal or proximal, and symmetric or asymmetric?
• weakness without sensory changes points toward motor neuropathy, neuromuscular jxn disorder and myopathy, and points away from neuropathy
• numb, feel weak, paresthesias, dysesthesias, hyperpathia, allodynia, loss of proprioception

pain

• poorly localized, usually sharp and lancinating, can be dull
• burning, “on fire”, especially in the digits
• pain and temp loss, but intact vibrio/proprio and reflexes and strength, points toward small fiber neuropathy

autonomic symptoms
-changes in skin color + temp + hair, edema, fainting spells, heat intolerance, bowel/bladder/sexual dysfxn

symptoms of associated conditions
-DM, EtOH abuse, preceding infection

Question 4

PE FINDINGS

Answer 4

• mini mental status exam – not really see a lot should be normal
• involuntary movements –not seen
• bulk findings – if motor neuropathy
• Hypotone – low tone
• Strength – decreased
• Rapid movements/FTN/HTS with eyes open (cerebellum) – coordination should be normal
• RAM/FTN/HTS with eyes closed – proprioception problems in PN
• Romberg/Pronator Drift – proprioception problems in PN
• gait ataxia? – abnormal
• Light touch and PinPricking testing – abnormal
• Vibrio/Proprio testing – abnormal
• Stereognosis – testing cortical function – central nervous system – should be normal in PN
• Hyporeflexia seen in PN not hyperreflexia (CNS – upper motor neuron)
• Babinski – Negative because in CNS upper motor neuron test
• Hoffman’s – Negative tests for lesion in CNS

Question 5

Diabetic Mellitus PN

Answer 5

• mcc of PN (I call it DMPN)
• uncontrolled hyperglycemia affects many nerves, leading to many subtypes: distal sym sensory or sensorimotor (mc subtype), autonomic neuropathy, polyradiculoplexopathy, CN palsies, or other mononeuropathies (common for a diabetic to have carpal tunnel syn)
• DM distal sym sensorimotor PN (DMPN)
• ascending numbness: numb toes, then legs then fingers and hands (worst case gets into trunk) -> stocking-glove sensory loss seen on neuro exam.
• distal lower extremity weakness; probable EDB atrophy
• tingling + burning (neuropathic) pain
• demyelinating and axonal loss
• get blood glucose under control!
• DM Autonomic PN: abnl sweating, abnl temp control, sicca syn, abnl pupil control, gastroparesis (slow passage thru the guts -> constipation > diarrhea), impotence, urinary incontinence, orthostatic hypotension and cardiac arrhythmias
• DM Radiculoplexopathy (aka DM Amyotrophy): usually presents as back and one leg pain -> weakness/atrophy is distal muscles (tiny EDB in the foot) -> weight loss, will present as thoracic radiculopathy. Radiculopathy not assoc with diabetes almost never present in the thoracic spine.

Question 6

Vitamin B12 Deficiency

Answer 6

• causes include lack of gastric Parietal Cell production of Intrinsic Factor (due to absent stomach as in gastric bypass), vegetarianism, proton pump inhibitors/H2 blockers, inflam bowel dz and pancreatic insufficiency
• mc result of B12 def = Pernicious anemia (no Intrinsic Factor = no Vit B12 = insufficient RBC production).
• B12 def also results is Subacute Combined Degeneration
• vit B12 def affect the spinal cord, specifically dorsal column degeneration -> loss of vibrio/proprio
• also affects the brain and peripheral nerves (“combined”)
• hands before feet
• mainly a large fiber neuropathy -> altered vibrio/proprio -> gait ataxia
• usually no small fiber findings -> pt doesn’t have a lot of burning pain or light touch/PP loss.

Question 7

Charcot Marie Tooth PN

Answer 7

• mc type of hereditary neuropathies
• many subtypes based on inheritance patterns, but mainly on predominant pathology
• Type I: mcc; demyelinating sensorimotor; childhood
• Type 2: axon loss; childhood < early adult
• Type 3: sev demyelinating sensorimotor; infancy
• Type 4: demyelinating sensorimotor; childhood and early adult
• CMT type 1: distal weakness (foot drop) with peri-knee atrophy and hyporeflexia, usu no numbness or tingling (differentiates from other PNs)
• CMT type 2: similar to type 1 but later presentation
• CMT type 3: severely weak infant
• CMT type 4: rare

Question 8

Inflammatory/Immune Mediated

Answer 8

Acute Inflammatory Demyelinating -Polyradiculoneuropathy (AIDP, aka Guillain-Barre Syndrome)

• CIDP (chronic GBS)
• Assoc. with Multiple Myeloma or Monoclonal Gammopathy of Undetermined Significance (MGUS)
• Assoc. with Vasculitides (namely polyarteritis nodosa)

Question 9

Cancer Related (paraneoplastic)

Answer 9

• cancer invasion/compression of nerves
• remote (paraneoplastic) effect: cancer causes antineuronal antibody production, tumor cell protein antigens look like neuron antigens, so immune system attacks both cells
• toxicity d/t chemo or radiation
• immune compromise d/t immunosuppressants
• mcc CA-induced PN = lung CA
• mainly distal asym numbness/paresthesias with sensory -ataxia (ataxia d/t loss of proprio) and weakness

Question 10

Toxic

Answer 10

• chemotherapeutics: cisplatin, vincristine (any of the ‘vins’), suramin, ARA-C
• DMARDs”(hydroxy)chloroquine
• amiodarone (antiarrythmic)
• colchicine (gout)
• metronidazole (anti-fungals)
• elemental: Lead, mercury, thallium, arsenic, gold

Question 11

Mononeuropathy

Answer 11

• carpal/cubital/tarsal tunnel syndromes
• meralgia paresthetica (lat fem cutaneous entrapment neuropathy)
• femoral neuropathy post hip surgery
• common peroneal neuropathy (foot drop) post prolonged surgery d/t compression/malpositioning
• Trigeminal Neuralgia
• Bell’s Palsy

Question 12

Trigeminal Neuralgia

Answer 12

-epidemio: middle-late life; W>M
-etio: unclear (85% idiopathic)
-H+P: episodic, brief, lancinating facial pain in the trigeminal distribution. mc distribution is V2+V3
usually unilateral, worse with touch (even chewing, the wind [allodynia], speech), other CN exam normal
-DDx: MS (must r/o if pt is young), brain stem tumor, other atypical facial pain
-W/u: typically nl CT and MR (unless tumor)
-Tx: oxcarbamazepine or carbamazepine (must monitor CBCs, LFTs), 2nd line dilantin/phenytoin, baclofen, lamictal/lamotrigine, neurontin, steroid injection (refer to pain clinic)

Question 13

Bell’s Palsy

Answer 13

• epidemio: 70% all acute unilateral facial paralysis, M=F, except pregnant F, common in diabetics
• etio: unclear; cold, HSV/HZV/EBV/HIV/CMV/Lyme’s/syph; low genetics
• H+P: sudden onset, usually lasts <48h, full face unilateral paralysis +/- otalgia, +/- decreased taste and lacrimation, no other ear or CNS symptoms, did the patient have a recent infection, namely upper respiratory inf?
• DDx: stroke, tumor, infection, aneurysm/hemorrhage, meningitis
• W/u: CBC, ESR, BMP, LP for CSF studies?, RPR/HIV?, CT or MRI?
• Tx: steroids, antivirals, keep eye moist (patch?), surg referral if worrisome findings on imaging, optho?, ID?