Peripheral Neuropathies Flashcards by Sarah Gillen

Acquired peripheral neuropathies may arise from a variety of causes including metabolic, endocrine, infectious, immune-mediated, deficiency states, toxins, drugs, vascular, paraneoplastic manifestations, or idiopathic causes.

What are some common metabolic/endocrine causes of peripheral/polyneuropathies?

Diabetes mellitus

Thyroid disease

Uremia

Porphyria

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What are some infectious causes of polyneuropathies?

Mononucleosis
Hepatitis
Lyme disease
HIV
Leprosy
Syphilis
Herpes zoster

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What are some immune mediated causes?

GBS, CIDP, Miller Fisher

Multifocal motor neuropathy

Paraproteinemic (monoclonal gammopathy)

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What are some deficiency states that may play a role in developing a polyneuropathy?

B1, B6, B12, E, Copper

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What are some toxins that may cause peripheral neuropathy?

Alcohol

Metals: Pb, As, Hg, Th

Organic compounds: n-hexane, organophosphates

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What are some drugs that may cause polyneuropathy?

Vinca alkaloids (vincristine —> polyneuropathy in 100% of pts)

Phenytoin
Isoniazid
Amiodarone
Cis-platinum
Nitrofurantoin

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_____ deficiency causes a peripheral neuropathy that affects both the corticospinal tracts (+babinski) and dorsal columns (lose DTRs, neuropathy) of the spinal cord

B12

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What are some conditions associated with vascular causes of peripheral neuropathy?

RA
SLE
Polyarteritis nodosa

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Of the above, ________ causes are associated with pure sensory neuropathy (dorsal ganglionopathy)

Paraneoplastic

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Pure sensory polyneuropathies are rare. In these cases there are 2 classifications to be considered: Sensory ganglionopathy and small-fiber neuropathy

What are 2 underlying etiologies of a sensory ganglionopathy?

Paraneoplastic (search for occult malignancy)

Toxins (platinum based chemotherapeutics)

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Pure sensory polyneuropathies are rare. In these cases there are 2 classifications to be considered: Sensory ganglionopathy and small-fiber neuropathy.

What are the clinical features of a small-fiber neuropathy in terms of pain, temperature, light touch, reflexes, and strength?

Pain and temperature affected

Light touch, proprioception, reflexes, and strength are preserved!

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Signs and symptoms of small fiber polyneuropathy

Signs — decreased pin-prick and temp sensation, dysesthesias to light touch. Normal strength, reflexes, proprioception, vibratory sensation

Symptoms — pain, “burning” dysesthesias, paresthesias, temperature sensation abnormalities

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What are EMG findings with small fiber polyneuropathy? How is the diagnosis confirmed?

EMG/NCV is normal!

Dx based on skin biopsy — shows decreased epidermal nerve fiber density

[EMG is normal because small fibers are unmyelinated, and EMG only detects abnormalities of myelinated fibers]

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Most common identifiable cause of neuropathy in the US

Diabetes mellitus

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What are the different forms of polyneuropathy seen in DM?

Distal symmetric sensorimotor neuropathy (“stocking and glove”) — most common

Cranial neuropathy (CN III, VI, VII)

Mononeuropathy (carpal tunnel, etc)

Mononeuropathy multiplex

Autonomic neuropathy

Lumbosacral plexopathy (diabetic amyotrophy)

Radiculopathy

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Charcot Marie Tooth is a hereditary motor sensory neuropathy; what is the inheritance?

Autosomal dominant

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Differentiate Hereditary Motor Sensory Neuropathy type I vs. type II in terms of major pathologic feature and clinical presentation

[HMSN = Charcot-Marie-Tooth]

Type I = Most common; Demyelinating is major feature. Onset 1st or 2nd decade; often see difficulty walking or running, distal symmetric atrophy, arreflexia, mild sensory loss, skeletal deformities (pes cavus, hammer toes, scoliosis)

Type II = Axonal loss is major feature. Onset in adulthood; distal symmetric atrophy, arreflexia, mild sensory loss

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EMG findings with HMSN type I vs type II

Type I EMG — slowling of motor nerve conduction velocities (i.e., demyelination)

Type II EMG — normal or nearly normal motor nerve conduction velocities (i.e., axonal loss

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Hereditary polyneuropathy caused by alpha galactosidase deficiency

Fabry’s disease

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Hereditary polyneuropathy due to alrylsulfatase A deficiency

Metachromatic leukodystrophy

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Hereditary polyneuropathy due to deficiency in HDL

Tangier disease

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Refsum’s disease is a hereditary polyneuropathy also known as _______ _____storage disease

Phytanic acid

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Hereditary polyneuropathy due to defect in heme biosynthesis

Porphyria

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Globoid cell leukodystrophy, abetalipoproteinemia (bassen-kornzweig syndrome), and familial amyloid neuropathies are __________

A. Acquired polyneuropathies
B. Acquired mononeuropathies
C. Hereditary mononeuropathies
D. Hereditary polyneuropathies
E. None of the above

D. Hereditary polyneuropathies

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Acute/subacute ascending motor paralysis often following a viral syndrome (EBV, mycoplasma pneumoniae, C.jejuni enteritis), surgery, or immmunization

Guillain-Barre syndrome

Clinical features of GBS

Low back/leg pain possible at onset Ascending usually symmetric weakness Hypo or absent DTRs No/minimal sensory symptoms or signs Possible respiratory failure; autonomic involvement

Key lab findings in GBS involving CSF and NCVs

CSF: albumino-cytologic dissociation (increased protein, normal cell count, normal glucose) NCVs: slow conduction velocity, focal conduction block, prolonged F-waves

Treatment for GBS

General supportive care with attention to: swallowing, respiration, cardiovascular support, infection, DVT Direct treatment with plasma exchange or IVIG

Prognosis of GBS

25% need mechanical ventilator support 90% recover in weeks to months — 5-10% develop chronic form Death in 4-10% Persistent disability in 20% Persistent fatigue in 67% Poor prognosis is associated with NCV/EMG findings of low amplitude motor nerve responses and/or denervation as this implies axonal involvement

Guillain-Barre Syndrome variant characterized by triad of ophthalmoplegia, ataxia, and arreflexia, as well as facial weakness, dysarthria, dysphagia, and antibodies to GQ1b and GT1a

Miller-Fisher Syndrome

GBS variant characterized by GM1, GM1b, and GD1a antibodies

Acute motor axonal neuropathy (AMAN)

GBS variant characterized by GM1, GM1b, and GM1a antibodies

Acute motor and sensory neuropathy (AMSAN)

Similar to GBS but slower to evolve and more persistent (i.e., >2 mos); may occur de novo or as sequelae of GBS with progressive or relapsing course; 15% have a monoclonal Ab (IgM or IgG) and treatment includes IVIG, steroids, plasma exchange, and/or immunosuppressive agents

Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

Clinical features of multifocal motor neuropathy

Adults, M>F Initially in distribution of a single nerve Slowly progressive distal weakness of hands>feet No sensory signs/symptoms, no UMN signs

Lab findings in multifocal motor neuropathy (antibodies, EMG, CSF)

Elevated serum GM-1 antibody in 50-80% EMG shows conduction block or other demyelinating features CSF usually normal

Types of neuropathy seen in HIV

Distal symmetric polyneuropathy Acute inflammatory demyelinating polyneuropathy Chronic inflammatory demyelinating polyneuropathy

________ = dysfunction of the nerve root caused by structural or nonstructural conditions

Radiculopathy

________ refers to the skin area supplied by a single spinal nerve root

Dermatome

________ refers to the muscle group supplied by a single spinal nerve root

Myotome

________ refers to the area of bone supplied by single spinal nerve root

Sclerotome

Most common levels involved with cervical radiculopathy

C5-6 = C6 nerve root compression C6-7 = C7 nerve root compression

Most common levels involved with lumbar radiculopathy

L4-L5 = L5 nerve root compression L5-S1 = S1 nerve root compression

For a C5 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = scapula, shoulder Sensory =lateral arm Weakness = shoulder abduction DTR loss = possibly biceps, but that is more likely lost with C6

For a C6 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = scapula, shoulder, prox arm Sensory = 1st and 2nd digit; lateral arm Weakness = shoulder abduction, elbow flex DTR loss = Biceps +/- brachioradialis

For a C7 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = scapula, shoulder/arm, elbow/forearm Sensory = 3rd digit Weakness = elbow ext, wrist ext, finger ext DTR loss = triceps

For a C8 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = scapula, shoulder/arm, medial forearm Sensory = 4th and 5th digit Weakness = finger abduction, finger flexion DTR loss = finger flexors

For a L4 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = antlat thigh, knee, medial calf Sensory = medial calf Weakness = hip flexion, knee extension DTR loss = patella

For a L5 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = dorsal thigh, lateral calf Sensory = lateral calf, dorsum of foot Weakness = hamstrings, foot dorsiflexion, inversion, eversion DTR loss = none

For an S1 radiculopathy, where is the location of pain, sensory change, weakness, and DTR loss?

Pain = post thigh, post calf Sensory = postlat calf, lateral foot Weakness = hamstrings, foot plantarflex DTR loss = achilles

Dermatome landmarks for C6, C7, C8

C6 = thumb/index finger C7 = middle finger C8 = fourth/fifth finger

Dermatome landmarks for T1, T4, T10

T1 = medial forearm T4 = nipple line T10 = umbilicus

Dermatome landmarks for L1, L4, L5

L1 = inguinal L4 = medial calf L5 = lateral calf

With a brachial or lumbosacral plexopathy, routine nerve conduction studies are often not adequate to make the diagnosis. ______ nerve action potentials are abnormal (vs. radiculopathy). Paraspinal muscles must be examined. _______ and _______ muscles may identify more proximal lesions, so in these cases radiculopathy should be included in the differential

Sensory Rhomboids Serratus anterior

Causes of brachial plexopathy include compression/stretch (CABG), inflammatory/idiopathic (parsonage-turner), radiation injury, neoplastic, traumatic injury, and ischemia. How do you differentiate between radiation injury and neoplastic process as the cause of a brachial plexopathy?

Radiation —> upper trunk, lateral cord, PAINLESS Neoplastic —> medial cord, PAINFUL

Inflammatory/idiopathic brachial plexopathy characterized by severe pain in shoulder area followed within a few days by weakness and atrophy (as pain subsides); usually involving muscles of shoulder girdle. Spontaneous recovery occurs in 6-18 mos

Parsonage-turner syndrome

Peripheral nerve disease affecting sensory nerves does NOT typically manifest with loss of sensation. Positive findings more likely include _________ (if secondary to large myelinated fiber disease) or ______ (if secondary to small unmyelinated fiber disease)

Paresthesias; pain

Symptoms of peripheral nerve disease affecting motor nerves

Distal weakness Cramps Muscle fasciculations (twitching) Atrophy Decreased DTRs Reduced tone [note that peripheral nerve disease of motor nerves does not result in weakness, fatigue, areflexia, hypotonia, or deformity]

_____ nerve mononeuropathy is characterized by sensory loss involving medial palmar surface of lower forearm and palm, thenar eminence, thumb, and adjacent 2.5 fingers

Median

Clinical features of median mononeuropathy due to pronator syndrome

Insidious onset of diffuse/dull ache about the proximal forearm Pain exacerbated with forced forearm pronation Easy fatigue of forearm muscles Diffuse numbness of the hand mostly involving the 2nd-3rd fingers Absence of nocturnal awakening d/t pain or numbness

Nerve conduction and needle EMG results with median mononeuropathy d/t anterior interosseous syndrome

Nerve conduction: routine median and ulnar studies are normal Needle EMG — abnormalities in FPL, FDP, PQ, while other median, medial cord, C8 mm are normal

Common sites that cause ulnar mononeuropathy

Axilla Elbow — between medial epicondyle and olecranon Cubital tunnel — b/w tendinous arch of FCU Wrist — Guyon’s canal

With _____ mononeuropathy at the elbow, EMG may show abnormalities in 1st dorsal interosseous m., abductor digiti minimi m., adductor policis m., flexor carpi ulnaris m., and flexor digitorum profundus m.

Ulnar

What is Froment Sign?

Utilization of accessory hand muscles to grip sheet of paper — indicates ulnar neuropathy

Common sites causing radial mononeuropathy

Axilla — crutches Humerus/spiral groove — saturday night palsy (MOST COMMON) Supinator (posterior interosseous branch) Wrist (superficial radial sensory branch)

Radial nerve damage leads to readily recognizable ___ ___that results from paresis of the extensor muscles of the wrist, finger, and thumb

Wrist drop

Clinical features of radial mononeuropathy d/t spiral groove compression (saturday night palsy)

Weakness of wrist and finger extension Elbow extension (triceps) and brachioradialis SPARED +/- sensory loss dorsal thumb web [note: radial motor and sensory studies often normal; EMG findings in extensors of wrist and digits and perhaps brachioradialis]

What is the neuropathy: Weakness of foot dorsiflexion and eversion. Weakness of toe extension. Sensory loss dorsum of foot, +/- lateral calf

Peroneal mononeuropathy at fibular head

General blood tests performed to evaluate disease of peripheral nerves

``` CBC CMP Fasting BG ESR ANA, RF Thyroid function Serum protein electrophoresis Immunoelectrophoresis B12/Folate ``` [more specific tests based on hx and PE may include lyme Ab titer, ANCA, Anti-MAG, anti-GM1, Anti-GQ1b, Hu antibody]

T/F: EMG/NCV rarely leads to a specific diagnosis. The primary utility of these tests is to broadly classify into axonal or demyelinating disease

True [exceptions are GBS, CMT1, and MMN]

Skin biopsy is used to diagnose what type of neuropathy?

Small fiber neuropathy