peripheral nerve disorders
Post on 10-Apr-2015
691 Views
Preview:
TRANSCRIPT
Peripheral nerve disorders
Dr. Mehzabin Ahmed
Diseases of the peripheral nerves
Patients suffering from a peripheral nerve disease have
motor problems (muscle weakness) or
sensory disturbances (parasthesia, loss of sensation,
tingling, numbness) or
a combination of both.
Symptoms may be confined to one nerve or a group of
nerves in either symmetric or an asymmetric fashion.
Neuralgia is the pain in the distribution of a nerve or nerves eg. sciatica , shingles.
Neuritis is a term used to describe the inflammation of the nerves.
Neuropathy is a term used to describe the disturbed function or a pathological change in the nerve.
Trauma may also cause nerve injury, which is classified as: Neuropraxia- is a block in the nerve conduction through an
axon with no anatomical interruption in the continuity of the axon.
Axonotmesis-is the anatomical interruption of the axon with no or only partial interruption of the connective tissue framework.
Neurotmesis- is a complete anatomical disruption of the axon and all of the surrounding connective tissue (ruptured nerve).
General Clinical Patterns of Involvement
There are a variety of patterns that clinical symptoms
may manifest.
Mononeuropathy
Mononeuropathy multiplex or multifocal neuropathy
Polyneuropathy
This denotes focal involvement of a single nerve trunk.
A localized neuropathy usually implies a local causation, such as
trauma or nerve entrapment as in:
Ulnar neuropathy causes claw hand
Dorsal root ganglia in herpes zoster
Median nerve involvement- carpal tunnel syndrome
Facial nerve involvement- Bell’s palsy
Distal tibial nerve involvement- tarsal tunnel syndrome
Peroneal neuropathy- foot drop
In Leprosy, neuritis of any superficial nerve can be seen like the
median, ulnar, peroneal, facial nerve.
Mononeuropathy
Mononeuropathy multiplex or multifocal neuropathyThis denotes simultaneous or sequential involvement of two or more
nerves, usually not contiguously.
It implies local affection of multiple nerves, and may be due to a generalized process such as: Vasculitis- polyarteritis nodosa Multiple myeloma HIV Mixed cryoglobulinemia Mixed connective tissue disorder Sarcoidosis Multifocal CIPD (chronic inflammatory demyelinating
polyneuropathy) Leprosy Multifocal type of diabetic neuropathy Amyloidosis
Polyneuropathy
This is a generalized asymmetric involvement of peripheral nerves usually associated with a systemic disorder.
It is further classified as: Neuronopathy Myelinopathy Axonopathy
Neuronopathy
When the primary site of injury is the neurons, eg:
Poliomyelitis- anterior horn cells are involved Herpes zoster- trigeminal ganglion is affected Diphtheritic- sensory ganglia Carcinomatosis- as in paraneoplastic syndromes
Axonopathy Axonal degeneration occurs first Secondary demyelination is seen It is often symmetric in distribution, giving a "stocking-glove"
pattern of motor and/or sensory loss. Causes:
Diphtheria , Porphyria , Industrial chemical exposure, Drugs , Metabolic disease (diabetes mellitus, uremia), Nutritional deficiency of Vitamin B 2,6,12, Alcoholism , Hereditary motor and sensory neuropathies.
Myelinopathy When the primary event is the segmental demyelination with
the preservation of the axons.
Two main disorders that fall into this category are the Guillian
Barré syndrome and the chronic inflammatory Demyelinating
polyneuropathy.
These are immune disorders where antibodies reacting with
antigens present on the peripheral nerves elicit an
inflammatory reaction that destroys myelin and axons.
Other disorders are multiple myeloma, cancers, HIV, HMSN
(hereditary motor and sensory neuropathy)
Early peripheral neuropathy Late peripheral neuropathy
Classification of peripheral nerve diseases
The categories into which nerve diseases may fall.
Metabolic and toxic neuropathies
Vasculitic neuropathies
Inflammatory neuropathies
Hypertrophic neuropathies
Genetic neuropathies
Infectious neuropathies
Metabolic and toxic neuropathies Usually associated with axonal degeneration, with varying
degrees of secondary demyelination.
Causes:
Some of the metabolic disorders associated with neuropathy
include diabetes mellitus, vitamin deficiency, uremia, and
prophyria.
Exogenous toxins that have been associated with neuropathy
include alcohol, vincristine, isoniazid, arsenic, lead, hexane,
hexachlorophene, acrylamide, and triethyltin.
Inherited lysosomal storage disorders also have neuropathy
as a component of the systemic metabolic defect.
Vasculitic neuropathies Usually present as a subacute mononeuropathy multiplex,
or symmetric polyneuropathy
The lesions in peripheral nerve are due to ischemia, and
frank infarction may be present.
Causes:
Polyarteritis nodosa,
Churg-Strauss syndrome, and
Rheumatoid arteritis
Inflammatory neuropathies:
Immune mediated damage. Present as an acute paralytic illness.
Acute inflammatory demyleinating polyneuropathy, or Guillain-Barre syndrome, may present as an acute paralytic illness.
Chronic inflammatory demyelinating polyneuropathy has either a relapsing/remitting or chronic progressive course (may cause a severe disability, in chronic cases axonal loss may also occur in addition to the Demyelination).
Hypertrophic neuropathies
These disorders are united by a characteristic pathologic
feature - the presence of "onion bulbs”-multiple Schwann
cell processes concentrically surrounding either individual
or small groups of fibers.
This hypertrophy may be so severe as to cause palpable
enlargement of affected nerves.
Causes: Chronic relapsing polyneuropathies, where multiple bouts of
demyelination and remyelination occur; Long-standing diabetic neuropathy; and Genetically inherited conditions such as
Charcot-Marie-Tooth disease - Autosomal dominant disorder- weakness and atrophy of the distal muscles- especially those innervated by the peroneal nerve thus giving a stork leg appearance, - pes cavus, - sensory loss and action tremors. - slowly progressive and is compatible with a normal life,
Dejerine-Sottas neuropathy, Refsum's disease.
Hypertrophic neuropathies (contd)
Stork like deformity of the legs
Upper limbs and hands are involved in later stages
Pes cavus- high arched foot
Genetic neuropathies: A wide variety of disorders may be placed in this category, including the
inherited hypertrophic neuropathies described above, some forms of leukodystrophy (metachromatic leukodystrophy is one
example), ataxia-telangiectasia, and giant axonal neuropathy.
Infectious neuropathies: A wide variety of pathogens may infect nerve. More common causes include
herpes zoster neuritis, and in the third world, leprosy & poliomyelitis.
Shingles in Varicella-Zoster infection Thickened nerves in leprosy
Diabetic Neuropathies
Diabetic neuropathies are heterogeneous group of disorders
that may be clinically classified into 4 major groups:
1. Distal symmetric primarily sensory neuropathy
(polyneuropathy)
2. Autonomic neuropathy
3. Proximal asymmetric painful primarily motor neuropathy
(also known as diabetic amyotrophy)
4. Cranial mononeuropathy
Both diabetic polyneuropathy and the autonomic
neuropathy of diabetes are thought to be due to metabolic
abnormalities.
Chronic hyperglycemia activates the pathway in nerve
tissue that reduce the sodium-potassium-ATPase activity,
which is critical for nerve function.
Thus the nerve conduction is altered and eventually also
results in structural nerve changes, like demyelination - in
this case, it is a form of secondary demyelination.
Diabetic amyotrophy and cranial neuropathies are thought
to be due to focal ischemic lesions on the basis of the
vascular disease- diabetic microangiopathy
The most common neuropathy in clinical
practice is diabetic neuropathy
Inherited neuropathies They are rare and include
Lysosomal storage diseases,
familial Amyloidosis,
the neuropathies in these diseases is a component or
symptom of the systemic metabolic defect.
Diseases that cause neurogenic atrophy
Neurogenic atrophy occurs when there is interruption of the normal innervation of muscle.
This can occur at the level of the anterior horn cell, or the axon. the neuromuscular junction as with myasthenia gravis.
Many disease processes may result in neurogenic atrophy, like: Anterior horn cell disorders:
1. Poliomyelitis
2. Amyotrophic lateral sclerosis
3. In infants, spinal muscular atrophy, which is also known as Werdnig-Hoffman disease
Axonal abnormalities. These include peripheral neuropathies and traumatic transections. 20
Following the loss of innervation, myofibers atrophy and become small and angular.
The appearance of the entire muscle will depend upon the number of motor units involved in the initial injury.
If there is only partial denervation and only scattered motor units are involved, the initial stages of denervation atrophy will be characterized by scattered, atrophic myofibers This is because myofibers from an individual motor unit are randomly distributed throughout a muscle fiber.
When the nerve regenerates the reinnervated fibers regain their normal appearance.
With repetitive or severe denervation, entire fascicles of myofibers may become atrophic, producing the pattern of fascicular atrophy.
Spinal muscular dystrophy: Syn: infantile motor neurone disease
It is a congenital disorder inherited by the Autosomal recessive mode.
It begins in the childhood/ adolescence causing muscle weakness. Widespread atrophy is noted involving entire fascicles-
panfascicular with a few scattered enlarged myocyte fibres.Four main forms are seen Type 1: Werdnig- Hoffman disease- rapidly progressing form
sometimes present since birth or onset is before 3mths of age Type 2: More slowly progressing, seen in infants and children
between 6-12mths. It causes severe disability. Type 3: Kugelberg Welander disease- Slow progression with
onset at 2-15 years and lives upto adult life. The disability is mild to moderate.
Type 4: Very slow progression with mild disability. The patients are usually adults.the progression may stop after several decades.
Myasthenia GravisPathology and pathogenesis Myasthenia gravis is an autoimmune disorder presence of antibodies against acetylcholine
receptors in the neuromuscular junction, (IgG and C3 can be found at postsynaptic muscle membranes).
It is thought that antibodies to the acetylcholine receptor function either by blocking the receptor or by causing its degradation.
Clinical findings Myasthenia gravis is an autoimmune disease, clinically characterized by
muscle weakness and fatigability. Weakness is generally worst at the end of the day, and
particularly affects extraocular and facial muscles. The disease can be mild and restricted, or generalized,
catastrophic and fatal. There are two groups of susceptible individuals: young women their
twenties, and older men before the age of 70. Younger women tend to be HLA-B8 positive and have thymic
hyperplasia, older male patients are more likely to have thymoma and
characteristically worsening of symptoms with repetitive stimulation of motor nerves.
Patients will also show a response to anticholinesterase agents, which is the basis of the Tensilon test (with edrophonium, the patient improves).
Eaton-Lambert Syndrome
Eaton-Lambert syndrome is a syndrome in which patients display weakness in proximal limb muscles.
an improvement in the symptoms in response to repetitive stimulation on EMG.
impaired release of acetylcholine at nerve terminals. Eaton- Lambert syndrome is caused by antibodies directed
against calcium channels found on the surface of small cell carcinoma which cross-react with similar channels on presynaptic terminals
It is a paraneoplastic syndrome seen in small cell carcinoma
Summary
Terminology Patterns of peripheral nerve involvement
Mononeuropathy Multifocal neuropathy Polyneuropathy-
Neuronopathy Myelinopathy Axonopathy
Causes of PN Diseases: Metabolic & toxic neuropathies- diabetic neuropathy Vascular neuropathies Inflammatory neuropathies Hypertrophic neuropathies Genetic neuropathies Infectious neuropathies Inherited neuropathies
Neurogenic atrophy: Spinal muscular dystrophy Myaesthenia gravis Eaton- Lambert syndrome
Summary
top related