The cause of LRPN can be diabetic or nondiabetic; a diabetic cause is the most common.[4] CSF protein and glucose levels are lower in patients with nondiabetic LPRN than in those with diabetic LPRN. An MRI scan or a CT myelography reveals no structural lesion, and MRI of the lumbosacral plexus or spine inconsistently demonstrates contrast enhancement in the nerve root or plexus.[3] Treatment depends on the underlying cause.
GFAP is an intermediate filament protein that is expressed mainly in astrocytes but is also present in nonmyelinated Schwann cells. The GFAP gene is activated during traumatic brain and spinal cord injury.[9] The GFAP antibody was initially discovered in patients with idiopathic corticosteroid-responsive meningoencephalitis.[10] These antibodies have also been found in patients with idiopathic immune-mediated polyneuropathy that is responsive to corticosteroids.[11]
In this case, the patient received monthly intravenous methylprednisolone (Solu-Medrol), 1 g per day over 5 days, for 6 months, as well as chemotherapy. With both treatments, he had drastic improvement of his proximal lower-extremity strength and was able to ambulate with a walker.
LPRN is one of the immune-mediated peripheral nerve disorders. Many other conditions result in a similar presentation, with different prognoses and treatment modalities.
Guillain-Barré syndrome (GBS) is a rapid, progressive immune-mediated polyradiculoneuropathy that is associated with profound weakness, sensory loss, and hyporeflexia. Facial weakness, respiratory impairment, severe neuropathic pain, and autonomic dysfunction have also been reported.[12] It is typically preceded by an infection 10-14 days earlier. The most commonly associated pathogens include Campylobacter jejuni, followed by Mycoplasma pneumoniae, Epstein-Barr virus, hepatitis E virus, cytomegalovirus, enteroviruses, and influenza A virus.[13,14] Symptoms peak at 4 weeks.
The diagnosis is confirmed by electrodiagnostic testing, with prolonged or absent F waves (within 1-2 weeks) and a normal sural response but a reduced sensory response in other nerves. After 3 weeks, primary demyelinating features (partial motor conduction block, temporal dispersion, nonuniform slowing) become apparent. CSF analysis shows cytoalbuminologic dissociation (an elevated protein level with a normal cell count).[15] MRI frequently demonstrates hypertrophic nerve roots, with preferential involvement of the anterior spinal roots, and contrast enhancement.[16]
Intravenous immunoglobulin (IVIG) (2 g/kg divided over 2-4 days) and plasma exchange (four to six sessions on alternate days) are first-line acute treatments with equal efficacy.[17] Supportive management, with close monitoring of respiratory function and for detection of cardiac arrhythmias, as well as physical and occupational therapy and neurorehabilitation, are essential to the long-term outcome.[18] Symptoms fluctuate within the first 2 months of onset and continue to improve afterward.
Many GBS variants have similar presentations:
Miller-Fisher syndrome presents with rapidly progressive ophthalmoplegia, ataxia, and areflexia, and most often follows C jejuni or Haemophilus influenzae infection.[19]
Bickerstaff brainstem encephalitis presents with hyperreflexia, ophthalmoplegia, and ataxia, with impaired consciousness.
Acute autonomic sensory neuropathy presents with sensory and autonomic deficits, without weakness. There is insufficient evidence to support immunotherapy in affected patients.[20]
Acute motor axonal neuropathy presents with rapid progressive weakness but intact sensation and deep tendon reflexes; acute motor and sensory axonal neuropathy presents with profound motor and sensory deficits. In both conditions, nerve conduction studies demonstrate axonal instead of demyelinating changes.
Unlike GBS and its variants, which are monophasic disorders, CIDP is an acquired demyelinating polyradiculoneuropathy. Both cellular and humoral mechanisms are involved in the inflammatory response.[21] Patients commonly present with symmetric proximal weakness that is greater than distal weakness, distal sensory loss, and hyporeflexia, with sparing of the cranial nerves, respiratory muscles, and autonomic function. Electrophysiologic testing shows prolonged distal motor and sensory latencies, slowed motor conduction velocities, prolonged minimal F-wave latencies, partial motor conduction block and abnormal temporal dispersion, and a sural-sparing pattern.[22] As in patients with GBS, MRI may demonstrate hypertrophic nerve roots, plexus, or proximal nerves with contrast enhancement.[23]
First-line treatment includes IVIG (2 g/kg divided over 2-5 days, followed 1 g/kg every 3-4 weeks) or subcutaneous immunoglobulin (0.4 g/kg/week for 5 weeks, followed by 0.2 or 0.4 g/kg weekly). Plasmapheresis may be considered for refractory cases. Corticosteroids in conjunction with mycophenolate and azathioprine may be considered as well.[24]
CIDP has many variants:
Multifocal motor neuropathy is an acquired demyelinating motor neuropathy. Patients present with wrist or foot drop without sensory loss. Motor nerve conduction studies reveal partial motor conduction block. Antibodies to ganglioside GM1 (anti-GM1 antibodies) are present in 50% of cases.[25] First-line treatment is IVIG; cyclophosphamide and rituximab may be considered for refractory cases. Corticosteroids have been reported to worsen the disease.[26]
Some patients who meet diagnostic criteria for CIDP have antibodies against contactin-1 and neurofascin-155. Both variants are refractory to IVIG but may respond to rituximab and are associated with demyelinating disease of the central nervous system. CSF protein levels are markedly higher in these variants than in CIDP.[27]
Distal acquired demyelinating symmetric disorder presents with slow, progressive distal sensory loss and is associated with anti-myelin–associated glycoprotein antibody.
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Cite this: Xuan Kang. Neurology Case Challenge: A Man With Buttocks Pain, Bladder and Bowel Incontinence - Medscape - Jul 21, 2022.
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