[On the Differential Diagnosis of Intractable Psychogenic Chronic Cough: Neuropathic Larynx Irritable - Gabapentin's...

We present the case of a 76 year old female inpatient who suffered from a chronic intractable cough which arose simultaneously to a severe major depression and was secondary to an exorbitant psychological distress. Chronic cough had never been experienced before and was initially considered to have a mere psychogenic origin since a comprehensive and guideline-based diagnostic screening did not reveal any underlying somatic cause. However, several factors cast doubt on the solitary psychic genesis of the chronic cough: i) occurrence immediately after a penetrant cold, ii) embedding in other complaints of laryngeal hyperreagibility (larynx irritable), such as persistent globus pharyngeus sensation, throat clearing and episodic dysphonia, iii) first occurrence on old life, iv) erupting from sleep as well, v) persistence despite remission of the major depression, and v) no sustaining benefit from specific psychotherapy and speech therapy. Therefore, diagnostics were extended to apparative tools for objective evaluation of swallowing by using fiberoptic videoendoscopic (FEES) and videofluoroscopic (VFS) techniques, which revealed signs of laryngeal neuropathy but without evidence of penetration or aspiration. A co-existing small goiter and an impaired glucose tolerance along with a putative intracellular vitamin B12 or folate deficiency (as indirectly derived from an apparent hyperhomocysteinemia) were assumed to be responsible for the neuropathy and underwent specific treatments. The impaired glucose tolerance and putative vitamin deficit were compatible with a distal symmetric sensorimotoric, even subclinical polyneuropathy of the lower extremities. The larynx irritable improved under gabapentin being confirmed by drug removals several times, and finally calmed down almost completely under gabapentin, which was in line with the scant literature of this topic. Re-examination of the larynx per FEES nine months later showed no deficits any more under the well-tolerated treatment (gabapentin, levothyroxine, vitamin B12 and folic acid substitution, weight reduction and physical training). All in all, the larynx irritable as well as the chronic cough were most probably induced by a laryngeal neuropathy and were not solely of psychic origin. Due to good treatment options a larynx irritable should be regularly taken into consideration of the investigation of intractable chronic cough. Therefore, an apparative evaluation of deglutition is recommended in the diagnostic toolbox of chronic cough - even if embedded in a psychiatric disorder or distress - before diagnosing a sole psychic origin. An hypothetical scheme of the development of a larynx irritable caused by neuropathic and non-neuropathic ("nociceptive") conditions is proposed.