Examination
In addition to a full neurological examination with particular attention to absent reflexes, the following points should be considered:
- Look for muscle wasting documenting whether the distribution is distal (hands and feet) or proximal (hips and shoulders) and symmetrical or asymmetrical.
- Look for fasciculation, indicating a lower motor neurone problem, often indicating damage/degeneration of the cell body (anterior horn cell).
- Look for pes cavus and claw toes; evidence that peripheral neuropathy has been present since early childhood and produced developmental deformity.
- Look for associated skin and nail changes. These may be seen in, for example, diabetes or a vasculitic process which may produce a multiple mononeuropathy.
- Palpate nerves to look for evidence of thickening as can be seen in leprosy.
- Detail the pattern of weakness noting whether it is distal or proximal and symmetrical or asymmetrical.
- Reflex testing is crucial. However, note that patients often have types of peripheral nerve dysfunction not causing a loss of reflexes (e.g. most times in mononeuropathy or multiple mononeuropathy and in polyneuropathy of a small fibre type).
- Sensory testing should include various modalities to contrast different fibre types and pathways, for example pinprick sensation versus proprioception and vibration sense.
- Draw out areas of reduced sensation to determine if this maps to a single root (dermatome) or single nerve, for example sensory disturbance in the medial portion of the palm and in the little and medial half of the ring finger in case of ulnar nerve entrapment at the elbow.
Investigations
Nerve conduction studies (NCS) help differentiate whether a single nerve is involved or multiple single nerves or a more generalised polyneuropathy. Similarly, whether the problem is exclusively in sensory nerves, motor nerves or a combination can be determined. By assessing the velocity of conduction and amplitude of conduction, it can be understood if the axon or the myelin sheath is predominantly affected.
Extensive blood testing: To look for causes of secondary generalised polyneuropathies particularly as identifying such causes may result in reversal of symptoms or at least halting of progression. A typical screen (depending on the history and examination) includes glucose, FBC, B12, U & E, LFT, Ca, TFT, CRP, PV, autoimmune profile, ACE, immunoglobilins, serum electrophoresis and urine for Bence Jones protein. In addition, infections may be looked for, including HIV, syphilis, lyme, chronic hepatitis and in cases of suspected paraneoplastic process test for paraneoplastic antibodies.
Lumbar puncture is helpful in specific situations, for example, in demyelinating neuropathies like Guillian–Barré syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP), where a raised CSF protein is typically seen (see later).
Management
Identifying the cause is the most important management step as it may allow cure or a halting or limiting of progression (e.g. managing diabetes more closely in diabetic neuropathy; reducing alcohol intake in an alcohol-induced neuropathy; median nerve decompression in CTS or treating GBS with intravenous immunoglobulin (IVIG)).
If irreversible or a cause is not identified, generic symptomatic treatments are employed to reduce neuropathy-related discomfort and pain such as amitriptyline or certain anticonvulsant medications.
A multidisciplinary team (MDT) approach to optimise aspects such as foot care and walking aids and treatment of autonomic dysfunction is also important.
Differential Diagnoses
It is important to consider that the sensory disturbance, motor weakness or autonomic failure observed may not be due to a peripheral nerve disorder but rather due to a central problem (brain/spinal cord) or in some cases due to isolated weakness related to disturbance of neuromuscular junction, for example Myasthenia gravis or in some other cases due to isolated muscle pathology, for example myositis.
Guillain–Barré Syndrome
Definition
It is an acute inflammatory demyelinating polyradiculoneuropathy. In approximately 10% of patients, however, the acute neuropathy is axonal rather than demyelinating. It is typically a monophasic, predominantly motor polyradiculopathy. By definition, such acute polyneuropathies reach maximal severity within 4 weeks.
Epidemiology
GBS is more common in the elderly, although it occurs at any age and in both males and females. GBS is the commonest cause of an acute peripheral paralysis.
Aetiology
Close to two-thirds of patients have had an infection during the preceding 6 weeks. Most often this is a respiratory tract infection but if gastrointestinal, Campylobacter jejuni is the commonest cause.
Pathology/Pathogenesis
GBS is an autoimmune disease triggered by preceding infection.
History
Pain in the lower back is often the first symptom. Initial weakness may be proximal, distal or both and may progress in either a descending or ascending fashion. Sensory disturbance is common. The face and bulbar muscles are often affected.
Examination
- Tone may be normal or reduced.
- Reflexes are characteristically lost but may remain present early in the condition.
- Sensory testing must be performed.
- Autonomic disturbance must be looked for and monitored (pulse, blood pressure and heart rhythm) as arrhythmias and hypotension or hypertension may result. The autonomic nervous system is affected to varying extent in this condition.
Investigations
- Nerve conduction studies may be normal during the first few days but then demonstrate slowing of motor nerve conduction and partial conduction block in the demyelinating form of GBS or reduction in compound muscle action potentials with preserved conduction velocity in the axonal form of GBS.
- CSF often shows an increased protein level but may be normal early on. The white cell count is normal or only minimally raised <10, i.e. the so-called albuminocytologic dissociation is usually observed.
- IgG antibodies to ganglioside GM1 are present in a quarter of patients, more often in those with acute motor axonal neuropathy.
- It is important to consider the other differentials for an acute polyradiculoneuropathy, including infective, toxic, metabolic or vasculitic causes.
Management
First consider life-threatening complications: measure vital capacity and assess bulbar function, monitor heart rhythm for arrhythmias, blood pressure for sudden surges or falls and administer DVT/PE prophylaxis.
IVIG is the mainstay of treatment. An alternative is plasma exchange; steroids are not helpful.
Ventilatory support in the intensive care unit may be required along with management of any autonomic disturbance.
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