Hyperacute Guillain-Barré Syndrome: A Pathophysiological Interpretation

To the Editor I read with great interest the paper by Matsubayashi and colleagues concerning a 36-year-old patient with classic Guillain-Barré syndrome (GBS), who presented with rapidly progressive lower-limb weakness and, to a lesser degree, in the upper limbs, which reached its nadir at 16 h after onset (1). Deep tendon reflexes were absent in all four extremities. Peripheral nerve conduction studies (NCSs) performed on the day of admission revealed bilateral decreased F-wave persistence in the common peroneal and tibial nerves. The remaining conventional motor and sensory nerve conduction parameters were normal. Seventeen days later, in the follow-up NCS and in comparison to the initial study, there was a reduction in compound muscle action potential amplitudes in both the tibial and peroneal nerves, and their motor conduction velocities were minimally slowed. A diagnosis of acute motor axonal neuropathy was made. I wish to offer some thoughts on the mechanisms that justify the findings in the initial NCS and those that account for upper-limb areflexia observed even when muscle weakness was barely detectable.

In very early classic GBS (≤4 days after onset), the predominant pathological background is inflammatory edema of proximal nerve trunks especially where motor and sensory roots join to form spinal nerves; such histological features have been corroborated by nerve ultrasonography (2). In spinal nerves with a relatively inelastic epineurial envelope, edema can cause an increase in endoneurial fluid pressure, which when sufficiently critical might compromise transperineurial blood flow, causing endoneurial ischemia with the corresponding local conduction failure (3). Under these circumstances, as described in the reference case, there may be a selective alteration of late waves (F-waves and H reflex) when there are no other changes in the NCSs.

As observed in the patient reported by Matsubayashi et al. (1), areflexia is a core and early feature of GBS, even when NCSs show normal motor and sensory conduction parameters, and there is still no overt motor weakness. Early GBS areflexia may be caused by the predominant involvement of a group of Ia afferents, with relatively preserved cutaneous afferents. There is evidence that in the hallmark of peripheral nerve disorders, Ia afferent fibers may exhibit variable vulnerability ranging from preferential involvement, as in GBS, to preservation, as in cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (4).

The author states that he has no Conflict of Interest (COI).