Answer to the letter to the editor of R. Nardone et al. concerning “Hepatic myelopathy with spastic paraparesis: report of two cases and review of the literature” (by Sana Ben Amor et al. (2013), Eur Spine J; DOI 10.1007/s00586-013-2828-z)

We would like to thank Drs. R. Nardone et al. for their comments. We are in agreement that the motor evoked potentials (MEP) elicited by transcranial magnetic stimulation may be helpful in the diagnosis of hepatic myelopathy especially in patients with chronic liver disease associated with a portosystemic shunt [1]. But we think that MEP is not specific for this pathology. MEP is a sensitive method to detect abnormalities of corticospinal pathways even in the absence of radiological changes [2]. In the event, myelopathy was the presenting manifestation we think that in such situation MEP could not be helpful for diagnosis of hepatic myelopathy. So, the diagnosis of hepatic myelopathy should be considered when all the other possible diagnoses were ruled out such as infectious or paraneoplastic myelopathy and degenerative diseases [3]. On the other hand, MEP could be abnormal in cirrhotic patients before hepatic encephalopathy is clinically manifesting [4]. This complication is more frequent than hepatic myelopathy in patients with chronic liver disease [1].