Frequency and Etiologies of Peripheral Type Cranial Neuropathy in the Neurology Inpatient Clinic.

Introduction: Peripheral type cranial neuropathies (PCNP) other than idiopathic peripheral facial paralysis are quite rare. In this study, we analysed patients with PCNP who were treated in our inpatient clinic. Methods: The patients who were hospitalized, examined and treated in our clinic between 1/1/2018 and 31/12/2023 were examined retrospectively. Sixty-three (34 men) out of total 3593 patients were found to have isolated PCNP. Demographic data, aetiologies, cerebrospinal fluid (CSF) findings, treatments and course of these patients were documented. Results: The average age of the patients was 56.25±15.55 years. Forty-three patients had single (unilateral/bilateral) and 20 had multiple PCNP. The most common involvement was seen in the VI. cranial nerve (24 isolated, 16 with other cranial neuropathies). The most common etiology was autoimmune/inflammatory (25 patients), followed by peripheral nerve ischemia (23 patients), infectious (6 patients), and tumoral infiltration (5 patients). Two patients with multiple PCNP had tumoral infiltration, Herpes infection in 2, COVID-19 in 2, Brucellosis in 1, and tuberculous meningitis in 1. Ischemic causes were most commonly associated with diabetes-related microvascular damage. Magnetic resonance imaging (MRI) examination revealed tumoral infiltration in 5 patients. Other MRI findings were cavernous sinus involvement and contrast enhancement of cranial nerves. CSF was examined in 53 patients; CSF protein was high in 20; pleocytosis was observed in one. Conclusion: Among peripheral cranial nerves, VIth is the most commonly involved, alone/together with other cranial nerves (CN). Inflammatory causes most commonly play a role in the etiology of PCNP. Malignancy and infectious etiologies should be considered first in patients with multiple cranial neuropathies (CNPs).