Guillain-Barré syndrome (GBS) is an acute autoimmune polyradiculoneuropathy, presenting as areflexic, flaccid paralysis with variable sensory disturbances, and elevated cerebrospinal fluid (CSF) protein without pleocytosis.[¹] The 2 features essential for a diagnosis of GBS are progressive motor weakness and areflexia. There are 2 distinctive pathologic subtypes of GBS: demyelinating and axonal. Recently, there have been several descriptions of reflex preservation and hyperreflexia in axonal GBS in Chinese, Japanese, and European populations.[^{1, 2}] Although this variant is not common in the Indian subcontinent, a few cases have been reported.[^{3, 4}] A high index of suspicion is needed to diagnose this rare presentation of GBS. We report 2 such cases discussing the pathophysiology and management aspects.

GBS is a group of syndromes with several distinctive subtypes classified on a pathologic basis into demyelinating and axonal forms. Axonal GBS has been classified further into 2 groups: AMAN and acute motor and sensory axonal neuropathy.[³] Although hyporeflexia or areflexia is the hallmark of GBS, normal reflexes or hyperreflexia is not a finding inconsistent with the diagnosis of GBS. The variants most commonly reported to be associated with retained or brisk reflexes are AMAN, acute motor conduction block neuropathy, and acute facial diplegia with brisk reflexes.[^{1, 5, 6}] The incidence of hyperreflexia in AMAN is reported to be between 33% and 48%.[^{1, 2}]

Hyperreflexia is seen in GBS associated with antecedent C. jejuni infection; most of them have history of abdominal pain and diarrhea. These cases are usually mild and significant bulbar or respiratory involvement is uncommon. CSF analysis shows albuminocytologic dissociation in most cases. Almost all of them have IgG anti-GM1 ganglioside antibodies although anti-C. jejuni antibodies are frequently negative.[¹] Antibody testing is not freely available in developing countries, such as India, which makes the diagnosis more difficult.

Although preservation of reflexes may simply be due to sparing of the sensory afferent pathway, the occurrence of brisk reflexes suggests a central mechanism. Dysfunction of inhibitory systems in the spinal interneurons has been proposed.[¹] In these cases, distal conduction disturbance, not axonal degeneration, produces low motor responses on nerve conduction studies, termed as reversible conduction failure or acute motor conduction block neuropathy.[²] The presumed mechanism producing reversible conduction block is impaired physiologic conduction at the nodes of Ranvier. One limitation of the study is that needle electromyography (EMG) examination was not done for both the cases. It would have strengthened the above hypothesis. None of the previous reports till date have done EMG in the above scenario.[^{1, 4}–⁶] Although in general, AMAN has been associated with extensive axonal loss and poor outcome, this subgroup with reversible conduction failure recovers rapidly.[^{1, 2, 6}] The response to both IVIg and large volume plasma exchange is similar. Both our cases also improved significantly at the end of 2 weeks.

The most common differential diagnosis presenting in a similar manner with acute progressive weakness and brisk reflexes is a high cervical myelopathy. Eliciting a careful history and a preceding history of enteritis, with electrophysiologic and CSF examination makes the diagnosis clear.

Therefore, GBS (axonal form) should be considered in patients with acute pure motor quadriparesis with normal or brisk reflexes, especially with antecedent gastroenteritis. This case report is to impress upon treating physicians and neurologists in training that a normo/hyperreflexic variant of GBS albeit rare, should not be missed in a given clinical setting.

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