Peripheral neuropathies are a group of very heterogeneous conditions. The clinical expression varies according to the affection and is translated either by a motor deficit with or without muscular atrophy, or by sensory disorders, or by a sensitivomotrice attack. The diagnosis, evoked from clinical data, is based on electrophysiological exploration.
– Clarifies the symptomatology (motor deficit, paresthesia), its intensity and topography, its impact in everyday life, its mode of installation and evolution.
– Clarifies personal and especially family history.
– Investigation of triggering factors (trauma, infectious episode, vaccination, drug or toxic intake).
He is looking for a peripheral neurogenic syndrome with presence of motor and / or sensory signs, abolition or decrease in reflexes.
The importance of paralysis is variable and it is classic to quote it:
Rating of paralysis
0 = no contraction
1 = weak contraction without displacement
2 = displacement if gravity is eliminated
3 = displacement despite gravity
4 = displacement against resistance
5 = normal muscle strength
Muscular atrophy, a consequence of denervation of the muscle, is often evident upon inspection. The topography will be analyzed through a comparative examination of different muscle groups.
– The fasciculations are visible at the time curling, spontaneous or triggered by percussion.Their presence directs towards an attack of the anterior horn of the marrow.
– Sensory disorders are variable depending on the type of fiber reached. A radicular or truncal systematization can be individualized, or a sock or glove involvement more suggestive of neuropathy.
– Osteotendinous reflexes are abolished or diminished, which sometimes makes it possible to specify the level of the lesion. There is no sign of Babinski except if associated pyramidal syndrome. Finally, the idiomuscular reflex obtained by direct percussion of the muscle is preserved.
– The search for an increase in the volume of the nerve on the back of the foot, elbow, or neck can lead to hypertrophic neuropathy (leprosy neuropathy, Refsum or Charcot-Marie-Tooth disease).
– Trophic disorders are observed in neuropathies with thermodouling and / or vegetative involvement: skin and integuments and at a more severe stage perforating diseases and osteoarticular lesions.
– Vegetative disorders Sweating disorders, especially, but also genital disorders, vesical, digestive, orthostatic hypotension or disorders of pupillary motility. This involvement is frequent in diabetic and amyloid neuropathy, porphyria but rare in polyradiculoneuritis.
EMG and study of conduction velocities:
They confirm that the deficit is related to a peripheral pathology.
They specify the neurogenic mechanism of the attack, either nerve damage (axon or myelin), or involvement of the cell body (motor neuron in case of motor impairment or ganglionopathy in case of sensory impairment).
They specify the topography. A mononeuropathy = attack of only one nervous trunk or root, a polyneuropathy = a diffuse and symmetrical attack, a multiple mononeuropathy = successive or simultaneous attack of several nerve trunks, roots or plexus.
Somesthetic evoked potentials and motors:
They complete the data in case of plexic or radicular involvement.
They are oriented by clinical and electrophysiological data: NFS, VS, metabolic balance, renal, hepatic, electrophoresis of proteins, search for a general disease, cryoglobulin, serology hepatitis, Lyme, HIV, thyroid hormones etc … In case of suspicion genetic disorder, a search for the gene involved is sometimes possible.
Radiological examinations: lumbar and cervical spinal MRI in case of radicular involvement.
Histological examinations: neuromuscular biopsy.
A neurogenic syndrome may be the result of damage to the anterior horns of the spinal cord (or the cranial nerve nuclei), nerve roots or peripheral nerves.
Motor neuron pathology:
– Acute anterior poliomyelitis was, before vaccination, the most common cause. Brutal installation after an infectious syndrome of a motor deficit without sensitivity disorders or pyramidal signs. Diagnosis is based on changes in CSF and identification of the virus.
– amyotrophic lateral sclerosis (Charcot’s disease): a neurodegenerative affection, of progressive evolution; association of a motor neurogenic syndrome with deficit, amyotrophy, cramps, fasciculations and a pyramidal syndrome without sensory involvement. It leads to the death of the patient in 3 years on average by bulbar involvement.
– Progressive spinal amyotrophy: progressive degeneration of the motor neurons of the spinal cord and sometimes of the brainstem, most often hereditary affections, some of which are localized. Several types are described according to the topography of the attack and the age of onset.
– Lesion syndrome (trauma, softening, compression, syringomyelia). The association of the peripheral involvement of a cranial nerve with a hemiplegia realizes an alternating syndrome and makes it possible to locate the level of the lesion in the brainstem.
The symptomatology can be pure motor, if the anterior root is only interested in the pathological process, but is usually sensitivomotor. It is traumatic, compressive, infectious or inflammatory; attack of a single root or several whose origin may be spinal but also plexic.
Pathology of the nerve:
Mononeuropathy: deficient motor or sensitivomotor symptomatology, limited to the territory of a single nerve (upper or lower limb). A traumatic or compressive mechanism is often involved, more rarely vascular damage in the context of general illness or an infectious cause such as leprosy.
– Multiple mononeuropathy: successive and asymmetrical involvement of several nervous trunks. Vasculitis is the most common etiology, diabetes as well. Shingles, brucellosis, AIDS are possible etiologies as well as haemopathies with or without dysglobulinemia.Electrophysiological exploration may suggest a dysimmune origin (antiglycolipids and antiGM1 antibodies). Finally, the presence of multiple ductal syndromes must make search for a genetic origin.
– Polyneuropathies: the etiological diagnosis of a polyneuropathy is difficult (more than a hundred identified causes) and many of them remain of unknown cause. The context in which neuropathy occurs can be a guiding element. The acute, subacute or chronic mode of installation is also an important element as well as the type of involvement (motor or sensory pure more or less associated with damage to the autonomic nervous system). Finally, the mechanism of the damage (axonopathy or myelinopathy) specified by the EMG, the topography of the deficit are also determining factors.
The ways in which the approach can be schematized according to the mode of installation, the axonal nature or the demyelinating nature of the attack are indicated in the table below:
In front of a polyneuropathy of acute installation:
– Acute poisoning (Lithium, thallium)
– Diabetic neuropathy
– Acute nutritional deficiency associated with alcohol intoxication
– Axon form of Guillain-Barré syndrome
– Vasculitis: a neuromuscular biopsy must be performed
Guillain-Barré type polyradiculoneuritis, the most common cause. To seek a hyperproteinorachie, to make a serodiagnostic of Campylobacter jejuni. The treatment is based on infusions of immuglobulins.
Diphtheric neuropathy is exceptional.
In front of a sub-acute installation polyneuropathy:
– Most likely diagnosis: metabolic, toxic or nutritional neuropathy: search for diabetes, hypothyroidism, renal failure, vitamin or nutritional deficiency associated with alcoholism.
– Toxic causes: industrial toxic or more often drugs (vincristine, amiodarone, isoniazid, almitrine, metronidazole, cis-platinum etc). We must also look for a systemic disease (sarcoidosis, necrotizing vasculitis, lupus), a hematological disease (hemo- and lymphoreticulopathies, dysglobulinemias), an infectious cause (hepatitis C with or without cryoglobulinemia, AIDS, Lyme disease), or even a primary amyloidosis .
– Subacute idiopathic polyradiculoneuropathy associated with hyperproteinorachia.
– Systemic lupus erythematosus.
– Gougerot syndrome.
– Conditional myeloma or solitary plasmocytoma or POEMS syndrome.
In front of a chronic polyneuropathy:
Acquired neuropathy associated with benign IgG monoclonal gammopathy.
– Hereditary neuropathy (axonal form of Charcot-Marie-Tooth disease).
The EMG makes it possible to guide the diagnosis:
– Chronic inflammatory polyradiculoneuropathy.
– Demyelinating form of Charcot Marie Tooth disease (search for genetic abnormalities).
– A slowing of the predominantly distal nerve conduction evokes an IgM dysglobulinemia with anti MAG activity.