approach to peripheral neuropathy
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Approach to peripheral
neuropathyDr. Parag Moon Senior resident
Dept of neurology GMC Kota
Generalized term including disorders of any cause affecting PNS
May involve sensory nerves, motor nerves, or both
May affect one nerve (mononeuropathy), several nerves together (polyneuropathy) or several nerves not contiguous (Mononeuropathy multiplex)
2
Definitions
Further classified into those that primarily affect the cell body (e.g., neuronopathy or ganglionopathy), myelin (myelinopathy), and the axon (axonopathy)
Most common causes
Disease Diabetes1 2
Paraproteinaemia2 3
Alcohol misuse1
Renal failure1
Vitamin B-12 deficiency1
HIV infection1
Chronic idiopathic axonal neuropathy4
Prevalence 11-41% (depending on
duration, type,and control) 9-10% 7% 4% 3.6%
16% (depending on the population studied, usually much lower)
10-40% of different hospital series
BMJ 2010:341:c6100
BMJ 2010:341:c6100
Loss of function“- symptoms”
Disordered function“+ symptoms”
Sensory “Large Fiber”
↓ Vibration↓ ProprioceptionHyporeflexiaSensory ataxia
Paresthesias
Sensory “Small Fiber”
↓ Pain↓ Temperature
DysesthesiasAllodynia
The clinical response to sensory nerve injury
Loss of function“- symptoms”
Disturbed function“+ symptoms”
Motor nervesLarge fibre
WastingHypotoniaWeaknessHyporeflexiaOrthopedic deformity
Fasciculation Cramps
The clinical response to motor nerve injury
Loss of function“- symptoms”
Disturbed function“+ symptoms”
Autonomic nerves ↓ SweatingHypotensionUrinary retentionImpotenceVascular color changes
↑ Sweating Hypertension
The clinical response to autonomic nerve injury
Mononeuropathy
Focal involvement of a single nerve and implies a local process:
Direct trauma compression or entrapment vascular lesions neoplastic compression or infiltration
Mononeuropathy multiplex
simultaneous /sequential damage to multiple noncontiguous nerves.
Ischemia caused by vasculitis Microangiopathy in diabetes mellitus Less common causes : Granulomatous,
leukemic, or neoplastic infiltration, Hansen's disease (leprosy) and sarcoidosis.
Polyneuropathy Characterized by symmetrical, distal motor
and sensory deficits that have a graded increase in severity distally and by distal attenuation of reflexes,
Rarely predominantly proximal:(E.g: acute intermittent porphyria).
The sensory deficits generally follow a length-dependent stocking-glove pattern
Axonopathies
By far the majority of the toxic, metabolic and endocrine causes
NCVs: CMAPs ↓ 80% lower limit of normal w/o or min velocity or distal motor latency change.
Legs>> arms. EMG: Signs of denervation (acute, chronic) and
reinnervation
Myelinopathies
Unusual by comparison with axonopathies Clues: hypertrophic nerves on exam
global arreflexiaweakness without wastingmotor >> sensory deficitsNCS can discriminate inherited from
acquired
NCS: Distal motor latency prolonged (>125% ULN)Conduction velocities slowed (<80% LLN)May have conduction blockEMG: Reduced recruitment w/o much denervation
Clues for diagnosis
Constitutional symptoms
DM hypothyroidism chronic renal failure liver disease intestinal
malabsorption malignancy connective tissue
diseases
[HIV] drug use Vitamin B6 toxicity alcohol and dietary
habits
•Weight loss, malaise, and anorexia.
Conditions Associated withPainful Peripheral Neuropathy Diabetes and Pre-Diabetes Alcohol neuropathy Chemotherapy
◦ Platinum-based Paraproteinemia Vasculitis and Connective Tissue Diseases Heavy metals and other toxins HIV Amyloidosis Porphyria
Medications Causing Neuropathies Axonal
Vincristine Paclitaxel Nitrous oxide Colchicine Probenecid Isoniazid Hydralazine Metronidazole Pyridoxine Didanosine Lithium Alfa interferon Dapsone
Axonal - continued..Phenytoin Cimetidine Disulfiram Chloroquine Ethambutol Amitriptyline
Demyelinating Amiodarone Chloroquine Suramin Gold
Neuronopathy Thalidomide Cisplatin Pyridoxine
Proximal Symmetric Motor Polyneuropathies
◦ Guillain-Barré syndrome◦ Chronic inflammatory demyelinating
polyradiculoneuropathy ◦ Diabetes mellitus ◦ Porphyria ◦ Osteosclerotic myeloma◦ Waldenstrom's macroglobulinemia ◦ Monoclonal gammopathy of undetermined significance◦ Acute arsenic polyneuropathy ◦ Lymphoma ◦ Diphtheria ◦ HIV/AIDS ◦ Lyme disease◦ Hypothyroidism◦ Vincristine (Oncovin, Vincosar PFS) toxicity
History The temporal course of a neuropathy varies,
based on the etiology.
◦ With trauma or ischemic infarction, the onset will be acute, with the most severe symptoms at onset.
◦ Inflammatory and some metabolic neuropathies have a subacute course extending over days to weeks.
◦ A chronic course over weeks to months is the hallmark of most toxic and metabolic neuropathies.
History A chronic, slowly progressive neuropathy
over many years occurs with most hereditary neuropathies or with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).
Neuropathies with a relapsing and remitting course include CIDP, acute porphyria, Refsum's disease, hereditary neuropathy with liability to pressure palsies (HNPP), familial brachial plexus neuropathy, and repeated episodes of toxin exposure.
Ischemic neuropathies often have pain as a prominent feature.
Small-fiber neuropathies often present with burning pain, lightning-like or lancinating pain, aching, or uncomfortable paresthesias (dysesthesias).
History
Dying-back (distal symmetric axonal) neuropathies initially involve the tips of the toes and progress proximally in a stocking-glove distribution.
History
Peripheral neuropathy can present as restless leg syndrome.
Proximal involvement may result in difficulty climbing stairs, getting out of a chair, lifting and bulbar involvement can also be seen
History
The clinical assessment should include:◦ careful past medical history, looking for systemic
diseases that can be associated with neuropathy, such as diabetes or hypothyroidism.
History
All patients should be questioned regarding ◦ HIV risk factors◦ diet (nutrition)◦ vitamin use (especially B6) ◦ possibility of a tick bite (Lyme disease) ◦ Constitutional symtoms (malignancy)
History
Differential Diagnosis of Neuropathies
by Clinical Course Acute onset (within days)
Subacute onset (weeks to months)
Chronic course/ insidious onset
Relapsing/ remitting course
Guillain-Barré syndrome
Maintained exposure to toxic agents/medications
Hereditary motor sensory neuropathies
Guillain-Barré syndrome
Acute intermittent porphyria
Persisting nutritional deficiency
Dominantly inherited sensory neuropathy
CIDP
Critical illness polyneuropathy
Abnormal metabolic state
CIDP HIV/AIDS
Diphtheric neuropathy
Paraneoplastic syndrome
Toxic
Thallium toxicity CIDP Porphyria
Physical Examination A cranial nerve examination can provide
evidence of mononeuropathies.
Funduscopic examination may show abnormalities such as optic pallor, which can be present in leukodystrophies and vitamin B12 deficiency.
Thickened nerves
Physical examination
Assessing Autonomic Nervous System
Cardiovagal◦ Heart rate variability
Adrenergic◦ Valsalva maneuver
Induces BP changes and monitors pulse reaction
Postganglionic sudomotor function◦ QSART
Recommendations for lab testing: Screening laboratory tests may be
considered for all patients with DSP (Level C).
Tests with the highest yield of abnormality:1. blood glucose (fasting)2. serum B12 with metabolites (methylmalonic acid, homocysteine)3. SPEP(serum protein electrophoresis)
(Level C).
Other laboratory studies ANA, RF, Anti-dsDNA, Anti-Ro, Anti-La, ANCA
screen, cryoglobulins Urine for heavy metals, porphyrins IFE/urine IFE/ plasma light chain analysis
Neuropathies + Serum Autoantibodies
Antibodies against Gangliosides GM1 : Multifocal motor neuropathy GM1, GD1a : Guillain-Barré syndrome GQ1b : Miller Fisher variant
Antibodies against Glycoproteins Myelin-associated glycoprotein : MGUS
Antibodies against RNA-binding proteins Anti-Hu, antineuronal nuclear antibody 1: Malignant
inflammatory polyganglionopathy
Electrodiagnostic studies
(1) Confirming the presence of neuropathy,
(2) Locating focal nerve lesions,
(3) Nature of the underlying nerve pathology
Distal motor latency prolonged
Nerve conduction velocity slow
Reduced action potential
The limitations of EMG/NCS should be taken into account when interpreting the findings. ◦ There is no reliable means of studying proximal
sensory nerves. ◦ NCS results can be normal in patients with
small-fiber neuropathies◦ Lower extremity sensory responses can be
absent in normal elderly patients.
EMG/NCS are not substitutes for a good clinical examination.
Laboratory Evaluation
Nerve biopsy In vasculitis, amyloid neuropathy, leprosy,
CIDP, Inherited disorders of myelin, and rare axonopathies
The Sural nerve is selected most commonly The superficial peroneal nerve – alternative;
:advantage of allowing simultaneous biopsy of the peroneus brevis muscle through the same incision.
This combined nerve and muscle biopsy procedure increases the yield of identifying suspected vasculitis
Skin biopsy
“For symptomatic patients with suspected polyneuropathy, skin biopsy may be considered to diagnose the presence of a polyneuropathy, particularly SFSN.”
Slow progression◦ Treat causative factors if possible◦ If rapidly progressing
IVIG Immunomodulating agents
Symptom Management
Treatment
Tricyclic antidepressants◦ Amitryptilin, nortryptilin
Calcium channel alpha-2-delta ligands◦ Gabapentin, pregabalin
Calcium channel blocker• Prialt SNRI’s
◦ Duloxetine, venlafaxine Topical Agents
◦ Lidocaine, Capsaicin
Symptom Management
Antiepileptic Drugs◦ Carbamazepine, phenytoin, lacosamide
SSRI’s Opioid analgesics Tramadol Miscellaneous
◦ Botulinum toxin◦ Mexiletine◦ Alpha lipoic acid
NMDA receptors unsuccessful◦ Namenda, Dextromethorphan
Symptom Management
First line drugs • Lidoderm 5% patch• Tricyclic antidepressants• Gabapentin• Pregabalin p.o.• Duloxetine Second line • Carbamazepine• Phenytoin• Venlafaxine • Tramadol
Physical Therapy ◦ Gait and balance training
Assistive devices Safe environment Footwear at all times Foot hygiene
Thanks
Clinical Approach to Peripheral Neuropathy: Anatomic Localization and Diagnostic Testing Adina R. Alport et al : Continuum Lifelong Learning Neurol 2012;18(1):13–38.
An Approach to the Evaluation of Peripheral Neuropathies;Mark B. Bromberg; SEMINARS IN NEUROLOGY/VOLUME 30, NUMBER 4 2010
References
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