Abducens Nerve Neuropraxia due to Acute Bacterial Rhinosinusitis: Case Report and Literature Review

Background Acute bacterial rhinosinusitis (ABRS) is a common infection of the paranasal sinuses that can lead to complications such as orbital and intracranial extension. The abducens nerve course is adjacent to the sphenoid sinus. Diplopia is rarely the initial presentation of sphenoid sinus pathology. In this article, we present the case of a middle-aged male who presented with diplopia and abducens nerve palsy secondary to ABRS, and we conducted a literature review in search of similar cases. Case Presentation. A 52-year-old male presented with diplopia secondary to ABRS. Imaging revealed the complete opacification of the bilateral sphenoid and frontal sinuses, with the extension of the inflammatory process to the optic nerve and cavernous sinus. The patient underwent a surgical intervention, which revealed a pyocele collection in the opticocarotid recess inside the sphenoid sinuses. After the surgery, the patient received antibiotics and reported a complete recovery. Conclusions Acute bacterial rhinosinusitis can present with atypical symptoms and lead to serious complications, such as abducens nerve palsy. Early diagnosis, appropriate management, and timely referral to a multidisciplinary team are crucial to preventing residual nerve damage and ensuring favorable outcomes.


Introduction
Acute viral rhinosinusitis triggers the activation of the immune cascade, which is responsible for common cold symptoms and helps to eradicate viral infection [1].In chronic rhinosinusitis (CRS), the prolonged infammatory reaction results in damage to the nasal epithelial cells' surfaces, as evidenced by altered protein expression [2].In acute bacterial rhinosinusitis (ABRS), these changes in the cell architecture compromise the defense mechanism of the cell, increase susceptibility to infection, and create a favorable environment for bacterial invasion [3].
Acute bacterial rhinosinusitis is clinically defned as the presence of any three of these signs and symptoms: purulent discharge, severe headache, fever, the elevation of infammatory markers such as the C-reactive protein/erythrocyte sedimentation rate, or double-interval illness [1].However, a meta-analysis showed that it is difcult to distinguish viral from bacterial acute rhinosinusitis in clinical settings and that the prevalence of ABRS remains poorly defned [4].
Te abducens nerve travels within the cavernous sinus, which makes it anatomically adjacent to the sphenoid sinus [5].Diplopia is rarely the initial presentation of sphenoid sinus pathology.Te abducens nerve can be afected by neoplasms, post-radiation changes, invasive fungal sinusitis, allergic fungal sinusitis, or bacterial sinusitis [6].In this article, we present the case of a middle-aged male who presented with diplopia and abducens nerve palsy secondary to ABRS, and we conducted a literature review in search of similar cases.

Clinical Presentation and Diagnosis.
A 52-year-old male with a body mass index of 26.5 and a known case of bronchial asthma and CRS presented to the emergency department, complaining of double vision for one day, which improved with the closure of the right eye.He had also been experiencing a severe right frontal headache for three days, nasal discharge, and facial heaviness.He denied having any other visual complaints, a history of allergic symptoms, or nasal obstruction.Te patient had two previous functional endoscopic sinus surgeries (FESSs), with the last having been completed in the tertiary center 18 months before presenting to the emergency department.Prior to his presentation, he had been using Mometasone nasal spray and normal saline nasal rinses for one month.
Te ophthalmological examination demonstrated binocular double vision during the straight and right gaze at near distances, with right extraocular muscle limitation of around 20%, indicating a partial right-sided sixth-nerve palsy.Other ophthalmic examinations, including visual acuity, intraocular pressure, and slit lamp examinations, were unremarkable.Meanwhile, the endonasal scope showed grade 2 polyps on the right side, with purulent discharge from the middle meatus.Te left side showed congested mucosa without polyps or purulent discharge.Te remainder of the cranial nerve examination was normal.Laboratory tests were unremarkable.
A computed tomography (CT) scan showed the homogenous complete opacifcation of the bilateral sphenoid and frontal sinuses.Erosion was seen within the anterior part of the right lateral sphenoid sinus wall, which was closely related to the superior orbital fssure.Tere was no skull base defect or dehiscence (Figure 1).A magnetic resonance imaging (MRI) scan showed mucosal thickening in all the paranasal sinuses, with increased central T1 signal intensity and decreased signal intensity on FLAIR and T2weighted images.A focal extension of signal abnormality was noted from the lateral aspect of the right sphenoid sinus, extending along the right superior orbital fssure, which was associated with mild dural thickening and enhancement in the anteromedial aspect of the right middle cranial fossa.Te extension of dural thickening and enhancement was also noted along the orbital apex surrounding the optic nerve (Figure 2).

Management and Surgery.
Te patient was given intravenous dexamethasone, clindamycin, and ceftriaxone for a duration of three days.On the ffth day of presentation, he underwent a revision bilateral endoscopic FESS, which revealed stenotic scarring on both maxillary antrostomies, with thick hydrated mucin and a polypoid fbrotic mucosa in the maxillary sinus, as well as multiple small pyoceles in the maxillary sinuses.Also, in the ethmoid cavity, the mucosa was polypoidal bilaterally and flled with small pyoceles.Ten, trans-ethmoidal sphenoidotomy revealed scar tissues sealing over right opticocarotid recess (OCR; Figure 3).It was opened, and the retained pus was suctioned to evacuate the retained collection.Dehiscence over the carotid and optic nerves was also observed.

Postoperative Management and Outcomes.
Te patient was discharged on the second day after the surgery, with close follow-up.His diplopia began to improve on the third day and then resolved completely on the eighth day of follow-up.He continued receiving oral antibiotics, a futicasone-salmeterol inhaler, and oral prednisone at 40 mg for 14 days, as well as normal saline irrigation and mometasone nasal spray postoperatively.On ophthalmological follow-up 2 months after surgery, the patient showed a full range of movement.Te endonasal scope revealed healthy-looking mucosa, including OCR.Te histopathology study of the surgical specimen demonstrated mucus and infammatory cells, and a bacterial stain and culture were negative, as was a fungal culture.Te patient has been followed up for the next 5 years, with no recurrence.

Discussion
Te sphenoid sinus is adjacent to critical structures, such as the middle cranial fossa, cavernous sinus, clivus and pons, cribriform plate, and posterior nasal cavity.It is separated from the surrounding structures by a wall barrier that consists of either thick bone, thin bone, or only mucosal membrane [7].A defect in the sphenoid sinus wall, which can be congenital or acquired, can lead to the extension of diseases to the surrounding cranial nerves and, thus, unfavorable outcomes [8].In particular, for the sphenoid sinus, the pattern of pneumatization may expand in diferent directions, with various extensions to adjacent structures, such  Case Reports in Otolaryngology as the optic nerve, cavernous sinus, the internal carotid artery, the frontal lobe, the ventral surface of the brainstem, cranial nerves III-VI, and the pituitary gland [9].One study found that the most common type of pneumatization is the lateral wall extension of the sphenoid sinus (29.5%), while the lesser wing type, which includes superior wall, OCR, and tuberculum recesses, was observed in only 7% of cases [10].Considering this, pneumatization can lead to a direct increase in sphenoid sinus pathology and extension to the surrounding structures.In our case, this presentation occurred following ABRS due to either the direct extension of the infammatory process from the infamed sinuses or the dehiscence of the abducens nerve in the OCR.Te course of ABRS is typically benign and self-limiting, and it can be managed with self-care measures such as analgesia, decongestants, and normal saline rinses.Oral antibiotics are recommended if symptoms do not resolve after 10 days or the severity of symptoms increases by the ffth day [1].Complications are rare and include orbital extension, which is thought to occur either directly through osteitis of the lamina papyracea or in a retrograde venous pathway via thrombophlebitis of the communicating veins [11,12].Te intracranial complications of ABRS exhibit a similar pathophysiology: the direct extension of osteitis from the frontal sinus, the extension of osteitis through a congenital or trauma-induced defect in the skull base, or retrograde thrombophlebitis of the diploic veins extending to the dura [13].Te presence of complications may encourage surgical intervention, specifcally the drainage of the sinuses to relieve pressure, rapidly remove the infammatory triggers, and isolate the organism and thus allow culturespecifc antimicrobial treatment.
If a patient presents with atypical symptoms of acute rhinosinusitis that indicate an extension beyond the sinuses, such as diplopia, stroke, or vision loss, this suggests a more aggressive disease, such as invasive fungal sinusitis.Te management of invasive fungal sinusitis requires systemic antifungal treatment, urgent surgical debridement of the necrotic tissue, and the reversal of the patient's immune status [1].
In patients with CRS, synechiae formation can be a sequel to the stripping of the mucosa during FESS.Tis complication is associated with more severe types of CRS    [14].Te presence of synechiae, as in our case, can alter sinus drainage, resulting in an encouraging habitat for bacteria and increasing the occurrence and severity of infections [15,16].Terefore, in modern FESS, mucosapreserving surgery is advised to avoid such complications and outcomes [15].Te pathophysiology of the acute exacerbation of CRS (AECRS) is believed to be triggered by a viral infection, most likely a rhinovirus, which, in turn, tends to increase the abundance levels of other microbial pathogens, such as bacteria.Tis infection activates the host infammatory pathway and promotes the classical manifestations of AECRS [1].In addition, the microbiological profle for AECRS is diferent from that of classical ABRS, and cultureguided therapy is recommended [17].However, only around 50% of patients suspected of having ABRS yield a positive culture [4].In our patient, the culture results were negative, which can be explained by the patient receiving antibiotics prior to the surgery.Some studies have identifed asthma, CRS without nasal polyposis, sinonasal outcome test scores greater than 24, a history of sinus surgery, a high body mass index, hay fever, and migraine as risk factors for AECRS [18,19].

Case Reports in Otolaryngology
Te most important prognostic factor for abducens nerve palsy depends on the underlying type of pathology and the extent of the damage to the nerve and blood supply.Destructive lesions involving the sinus wall and blood supply, such as invasive fungal sinusitis and invasive neoplasms, have been associated with poor recovery, while compressive masses without invasion have been associated with optimal recovery within two weeks [6].For abducens nerve palsy secondary to ABRS, the literature shows partial recovery in only three cases and no resolution in only one case of 24 [6,20,21] (Table 1).Te average duration of resolution for neuropraxia was 38.3 days (Table 1).Early intervention was found to be the most important factor in a favorable outcome and complete recovery, as delayed, proper intervention was associated with residual nerve damage [39].

Conclusion
Acute bacterial rhinosinusitis can present with atypical symptoms and lead to serious complications, such as abducens nerve palsy.Early diagnosis, appropriate management, and timely referral to a multidisciplinary team are crucial in preventing residual nerve damage and ensuring favorable outcomes.

Figure 1 :
Figure 1: Computed tomography imaging showing difuse opacifcation of the sinuses, with no skull base defect.

Figure 2 :
Figure 2: Coronal (left) and axial (right) T2 magnetic resonance imaging showed an abnormality from the lateral aspect of the right sphenoid sinus extending along the right superior orbital fssure.

Figure 3 :
Figure 3: An intraoperative endoscopic view of adhesion in the right opticocarotid recess (left) and the view after the release of the adhesions and the evacuation of the pus (right).

Table 1 :
Summary of cases of abducent nerve palsy secondary to sinus pathology in the literature.