HNP in general appears together with other neurological abnormalities in a large variety of diseases. A brainstem lesion frequently involves other nuclei or tracts, and a skull base lesion often affects other cranial nerves at the same time. Tumors are the predominant underlying condition of HNP . Vertebral artery dissection, nasopharyngeal cancer, Chiari malformation, and dural arteriovenous fistula are other known causes . These quite different etiologies emphasize the necessity of extensive medical assessment when confronted with a case of HNP, especially when postulating a diagnosis of idiopathic IUHNP.
Idiopathic IUHNP is believed to be an underreported condition which is more frequent than previously thought [6, 9]. Ahmed and colleagues found 13 single case reports . Most cases are reversible without any treatment and resolve within 2 to 4 weeks, though longer recovery periods between 2 to 5 months have been reported [1, 2, 6]. The persistence of symptoms in both our cases is unusual in idiopathic IUHNP compared to most other reported cases. Ho and colleagues described a case of idiopathic IUHNP that persisted over a period of at least 5 years and suggested a pathway of investigations to make the diagnosis of idiopathic IUHNP by way of exclusion . Two other cases of idiopathic IUHNP reported persistency of symptoms for a period of 36 months and 24 months respectively [4, 7]. Rarely, idiopathic IUHNP can be an early manifestation of an underlying demyelinating disease, and therefore, it has been recommended to do a repeat brain MRI scan every 3 to 5 years [3, 5].
The age of patients with isolated IUHNP varies a lot. The youngest reported patient was11 years old, while most other patients were between 25 and 81 years old . No clear specific age of onset is evident as well as there is no gender prevalence. To the best of our knowledge, our younger patient is the second reported having persistent idiopathic IUNHP at the age of 17 years.
It has been suggested by Lee and colleagues that idiopathic IUHNP is a clinical entity similar to Bell’s palsy (BP) . The use of oral steroids (OS) within 72 h of symptom onset in BP increases the likelihood of recovery of the facial nerve . In some case reports, OS have been used to treat idiopathic IUHNP, but a literature search revealed no clinical guidelines on the use of OS as a treatment option for this condition . As our patients were referred to us 1 month and 1 month and a half respectively after symptoms onset, with already visible tongue atrophy and fasciculation, we did not start OS treatment. Idiopathic IUHNP might involve speech and language impairment, and ST has been used as a rehabilitation method . Our first patient had no dysarthria, and no rehabilitation was required, while ST was implemented for the second patient, but without dysarthria improvement.
Thus, following the same pathway of investigation as suggested by Ho and colleagues, we presented two cases with persistent idiopathic IUHNP . IUHNP is a rare diagnosis with a challenging clinical presentation, and we recommend that physicians use a systematic approach to exclude severe underlying pathology or identify a treatable condition.