Differentials
Acute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP)
SIGNS / SYMPTOMS
Symptoms continue to progress 8 weeks after symptom onset. Can be difficult to differentiate initially; consider A-CIDP if patients show signs of worsening beyond 4 weeks.[15][91]
Other features suggestive of A-CIDP include marked sensory abnormality; absence of facial, bulbar, or respiratory weakness; and ≥3 treatment-related fluctuations.[15]
INVESTIGATIONS
Nerve ultrasound or MRI: may show widespread nerve enlargement.
Electrophysiological study: may show early significant reduction in motor nerve conduction velocity.
Antibodies against nodal-paranodal antigens (e.g., NF155, Caspr1, CNTN1) may be positive.[15]
Transverse myelitis
SIGNS / SYMPTOMS
Spinal cord disorders including transverse myelitis present with asymmetrical motor or sensory loss usually involving lower extremities, early bowel or bladder dysfunction with persistent incontinence, and segmental radicular pain.
Physical examination demonstrates upper motor neuron signs (hyper-reflexia, positive Babinski's response) and a sensory level.
INVESTIGATIONS
Cerebrospinal fluid analysis: pleocytosis with modest number of lymphocytes and increase in total protein.
MRI shows focal demyelination with possible enhancement at the appropriate level.
Myasthenia gravis
SIGNS / SYMPTOMS
Early involvement of muscle groups including extra-ocular, levator, pharyngeal jaw, neck, and respiratory muscles. Sometimes presents without limb weakness.
Excessive fatigability and variation of symptoms and signs through the day is common.
Reflexes are preserved, and sensory features, dysautonomia, and bladder dysfunction are absent.
INVESTIGATIONS
Electrophysiological study shows normal nerve conduction and presence of decremental response to repetitive nerve stimulation.
Electromyogram shows abnormal jitter and blocking.
Lambert-Eaton myasthenic syndrome (LEMS)
SIGNS / SYMPTOMS
Can be difficult to differentiate because of similar clinical characteristics.
Characteristics more typical of LEMS include slower development of clinical symptoms, dry mouth, lack of objective sensory loss, rare involvement of respiratory muscle group, and potentiation of reflexes after exercise or contraction.[151]
INVESTIGATIONS
Electrophysiological study: hallmark is a low amplitude compound muscle action potential (CMAP) after single nerve stimulus, increase in CMAP amplitude after voluntary contraction, or repetitive stimulation at high frequencies.[16]
Botulism
SIGNS / SYMPTOMS
History of ingesting food tainted with botulinum toxin.
Descending paralysis begins in the bulbar muscles then the limbs, face, neck, and respiratory muscles.
Respiratory muscles are involved with mild limb weakness, and reflexes are usually preserved.
Ptosis, dilated non-reactive pupils are present. Dilated non-reactive pupils are uncommon in Guillain-Barre syndrome (GBS), but more common in botulism.
Constipation is also a characteristic feature of botulism.
INVESTIGATIONS
Electrophysiological study: reduced amplitude of evoked muscle potentials, increase in amplitude with repetitive nerve stimulation, and increased number of myopathic units, which is atypical for GBS.[16]
Polymyositis
SIGNS / SYMPTOMS
Presence of pain and muscle tenderness usually in the shoulder and upper arm, involvement of flexor neck muscle disproportionate to limb weakness, absence of sensory symptoms, preservation of reflexes, absence of dysautonomia, and presence of skin lesions, which are uncommon presentation for Guillain-Barre syndrome.
INVESTIGATIONS
Elevated erythrocyte sedimentation rate and creatine kinase, normal nerve conduction study, and myopathic changes with fibrillation on electromyogram.
Muscle biopsy shows muscle fibre destruction and regeneration, and lymphocyte infiltrates.
Vasculitic neuropathy
SIGNS / SYMPTOMS
Common features include painful asymmetrical presentation of muscle weakness, uncommon involvement of cranial nerves, respiratory paralysis, and sphincter dysfunction.[152]
Usually patients report fever, fatigue, weakness, and arthralgia.
INVESTIGATIONS
May have elevated erythrocyte sedimentation rate.
Cerebrospinal fluid does not show albuminocytological dissociation.
Electrophysiological study shows evidence of denervation.
Nerve biopsy shows signs of inflammation and scarring.
Lyme disease
SIGNS / SYMPTOMS
Features include asymmetrical motor and sensory symptoms usually accompanied by pain. Cranial nerves are often involved, with facial nerves being most commonly affected. Weakness following a typical rash, fever, and arthritis in an endemic region should raise suspicion for Lyme disease.[153]
INVESTIGATIONS
Cerebrospinal fluid (CSF) fluids shows lymphocytic pleocytosis with raised protein.
Serological diagnosis includes testing for Borrelia specific IgM and IgG antibodies in serum.
CSF/serum IgG ratio of >1.3 has been used as a threshold for supporting diagnosis of neuroborreliosis.
Leptomeningeal metastasis
SIGNS / SYMPTOMS
The presentation is often non-specific as it can affect anywhere along the neuro-axis. Multifocal neurological symptoms in cancer patients should raise suspicion for leptomeningeal metastasis.[154]
The clinical signs and symptoms are variable depending on the neuroanatomy involved. They are often multifocal and include headache, cognitive deficits, gait disturbances, cranial nerve palsies, weakness, sensory symptoms, radicular pain, and faecal and urinary incontinence.[154]
INVESTIGATIONS
Cerebrospinal fluid (CSF) is often abnormal with significantly raised protein (>0.5 g/L [>50 mg/dL]) with raised cell count and opening pressures.
CSF cytology detects malignant cells.
MRI brain and spine with contrast is considered gold standard and often shows meningeal enhancement.
Leptomeningeal biopsies can be carried out to confirm the diagnosis.[155]
HIV-associated peripheral neuropathy
SIGNS / SYMPTOMS
Common features include burning pain, numbness, tingling sensation, and weakness in glove and stocking pattern. The spectrum of neuropathy includes distal pure sensory neuropathy, immune demyelinating neuropathy, toxic neuropathy, mononeuritis multiplex, cranial neuropathies, and polyradiculoneuropathy.[156]
INVESTIGATIONS
Cerebrospinal fluid is often abnormal with raised protein and cell count.
Diagnosis is often clinical, based on signs of neuropathy with history of HIV infection.[157]
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