Peripheral Neuropathies Flashcards
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
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 infectious causes of polyneuropathies?
Mononucleosis Hepatitis Lyme disease HIV Leprosy Syphilis Herpes zoster
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 immune mediated causes?
GBS, CIDP, Miller Fisher
Multifocal motor neuropathy
Paraproteinemic (monoclonal gammopathy)
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 deficiency states that may play a role in developing a polyneuropathy?
B1, B6, B12, E, Copper
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 toxins that may cause peripheral neuropathy?
Alcohol
Metals: Pb, As, Hg, Th
Organic compounds: n-hexane, organophosphates
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 drugs that may cause polyneuropathy?
Vinca alkaloids (vincristine —> polyneuropathy in 100% of pts)
Phenytoin Isoniazid Amiodarone Cis-platinum Nitrofurantoin
_____ deficiency causes a peripheral neuropathy that affects both the corticospinal tracts (+babinski) and dorsal columns (lose DTRs, neuropathy) of the spinal cord
B12
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 conditions associated with vascular causes of peripheral neuropathy?
RA
SLE
Polyarteritis nodosa
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.
Of the above, ________ causes are associated with pure sensory neuropathy (dorsal ganglionopathy)
Paraneoplastic
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)
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!
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
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]
Most common identifiable cause of neuropathy in the US
Diabetes mellitus
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
Charcot Marie Tooth is a hereditary motor sensory neuropathy; what is the inheritance?
Autosomal dominant
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
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
Hereditary polyneuropathy caused by alpha galactosidase deficiency
Fabry’s disease
Hereditary polyneuropathy due to alrylsulfatase A deficiency
Metachromatic leukodystrophy
Hereditary polyneuropathy due to deficiency in HDL
Tangier disease
Refsum’s disease is a hereditary polyneuropathy also known as _______ _____storage disease
Phytanic acid
Hereditary polyneuropathy due to defect in heme biosynthesis
Porphyria
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
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
