The abducens nerve (cranial nerve VI) is known for its very long travel from the brainstem to the ipsilateral lateral rectus muscle, where it provides an important function by stimulating abduction of the eye [1] [2]. But because the nerve is quite long, it can be damaged at various points along its pathway. In fact, abducens nerve palsy is one of the most frequent nerve palsies encountered in clinical practice, with an established incidence rate of 11.3 per 100 000 individuals [3]. Certain authors have divided the pathologies that cause abducens nerve palsy according to their anatomical sites (the brain stem, subarachnoid space, the petroclival region, the cavernous sinus, and the orbit), and numerous conditions, both localized and systemic, may cause this condition [1] [2]. The principal symptom of abducens nerve palsy is the presence of binocular horizontal diplopia, as the eye is not able to perform abduction, resulting in lateral displacement [4] [5]. In addition, many symptoms accompany sixth nerve palsy depending on the location of the lesion [1] [2] [4] [5]. For example, contralateral hemiparesis, ipsilateral palsy of the facial, but also trigeminal and vestibulocochlear nerves is seen in conditions affecting the brainstem, such as Raymond’s syndrome, Millard-Gubler syndrome and Foville’s syndrome [1]. Then, papilledema, visual deficits, and symptoms suggestive of a central nervous system (CNS) infection of any etiology (bacterial, viral, fungal) may be seen if the nerve is compromised in the subarachnoid space, as various tumors, sarcoidosis, pseudotumor cerebri and meningitis have been described as potential etiologies [1]. On the other hand, epistaxis, rhinorrhea, and serous otitis media, typically encountered in nasopharyngeal carcinoma, can also be seen together in abducens nerve palsy [1]. Other notable causes of this lesion include hypertension, diabetes mellitus, trauma, and several other tumors (meningiomas, acoustic neuromas, cerebellopontine angle tumors, and metastatic deposits), implying that a broad symptomatology could present together with abducens nerve palsy [1] [4] [5] [6].

• Nausea

  Our case lacked the typical symptoms of IIH, such as headache or nausea; therefore, it is necessary to carefully determine the cause of bilateral abducens nerve palsies. [ncbi.nlm.nih.gov]

  On the second day, the patient experienced nausea and vomiting. The nausea and vomiting did not respond to antiemetic medication. On the third postoperative day, headache, nausea and vomiting ceased completely but the patient complained of diplopia. [ispub.com]

  Patients may also present with other signs of increased intracranial pressure such as headache, nausea, vomiting or papilledema. [reviewofophthalmology.com]

  In cases of abducens nerve palsy due to raised intracranial pressure, patients may experience associated symptoms of headache, pain around the eyes, nausea, or vomiting. Associated pain suggests a microvascular etiology. [eyewiki.aao.org]

• Diplopia

  After dural closure, pseudomeningocele and headache resolved completely and diplopia improved partially. At 4-week follow-up, there was complete resolution of diplopia. [ncbi.nlm.nih.gov]

  To achieve complete resolution of diplopia, prism correction was used ( Fig. 2 ). Six months later, the vision of both patients remains stable, with no diplopia occurring while looking forward. [care.diabetesjournals.org]

  Her main complaint was diplopia on straight, upper, left, and lower gaze (Panels B through E). [nejm.org]

• Esotropia

  Primary outcome measures were esotropia in primary position and abduction deficit. [ncbi.nlm.nih.gov]

• Cranial Nerve Involvement

  Cranial nerve involvement in brucellosis is rare. We present a case of brucellosis presenting with optic neuritis and abducens nerve palsy on the left side. [ncbi.nlm.nih.gov]

  Examination for a sixth nerve palsy involves documenting the presence or absence of papilledema, examining the ocular motility, evaluating the eyelids and pupils, and excluding involvement of other cranial nerves (eg, V, VII, VIII). [emedicine.com]

• Focal Neurological Deficit

  Central nervous system involvement is very common and includes meningism, altered sensorium to focal neurological deficits. [ncbi.nlm.nih.gov]

The diagnosis of abducens nerve palsy is rather easy to make by conducting a proper physical examination that will include a complete assessment of eye muscles. It is necessary, however, to perform a thorough neurological examination, which might reveal other symptoms that could aid in determining the site of the lesion [2] [4]. After the examination, and a detailed patient history that will assess the course and progression of symptoms, imaging studies should be employed. Computed tomography (CT) is often performed as an initial method, but magnetic resonance imaging (MRI) of the endocranium is recommended for evaluation of the underlying cause of abducens nerve palsy, as it provides a more detailed view of the cranial structures [2] [5] [7]. Isolated reports have questioned its cost-effectiveness, however, since many patients in whom vascular diseases are responsible for the lesion improve spontaneously within a short period of time [5] [7]. Nevertheless, MRI is an effective method, while laboratory studies, including a complete blood count (CBC), a full lipid profile, glucose levels, erythrocyte sedimentation rate (ESR), antinuclear antibodies (ANA), and rheumatoid factor, are important in raising clinical suspicion toward vasculitis, diabetes mellitus and atherosclerosis [5]. Because infections and increased intracranial pressure (ICP) are also potential causes of abducens nerve palsy, a lumbar puncture with subsequent examination of the cerebrospinal fluid is recommended as well [1] [6].

However, despite a relatively long history of botulinum toxin treatment in ocular muscle paralysis ( 4, 6 ), its use and investigations of treatment with it in diabetic mononeuropathy have been less than scarce. [care.diabetesjournals.org]

After the exclusion of other organic lesions, especially idiopathic intracranial hypertension, and an assessment of the risk-benefit ratio, discontinuation of treatment must be considered in such cases. [ncbi.nlm.nih.gov]

Types of treatment Treatment of sixth nerve palsy depends on its cause. [fairview.org]

In conclusion, cranial nerve involvement in brucellosis can have good prognosis if anti-Brucella treatment is undertaken early. [ncbi.nlm.nih.gov]

Palsies related to trauma or brain masses have a guarded prognosis and recovery, if any, may take up to one year. [encyclopedia.com]

Long-term prognosis in patients with vasculopathic sixth nerve palsy. Am J Ophthalmol 2002; 134 : 81–84. 13 Patel SV, Homes JM, Hodge DO, Burke JP. Diabetes and hypertension in isolated sixth nerve palsy. Ophthalmol 2005; 112 : 760–763. [nature.com]

Conversely, slowly progressive onset suggests a compressive etiology. Subacute onset suggests a demyelinating process as a possible etiology. Associated pain suggests a microvascular etiology. [eyewiki.aao.org]

In many instances, the origin is obvious and management straightforward; however, the list of possible etiologies and mimics is vast and diverse and diagnostic decisions can be challenging and even controversial. [ncbi.nlm.nih.gov]

If no etiology is discovered on MRI or hematology studies, monitor the patient monthly for several months until resolution (or until other signs develop which would indicate an etiology). [web.archive.org]

[…] cerebri and meningitis have been described as potential etiologies. [symptoma.com]

Keywords: 590 strabismus: etiology • 354 clinical (human) or epidemiologic studies: prevalence/incidence • 400 esotropia and exotropia © 2002, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. [iovs.arvojournals.org]

Journal Journal ID (nlm-ta): Pan Afr Med J Journal ID (iso-abbrev): Pan Afr Med J Journal ID (publisher-id): PAMJ Title: The Pan African Medical Journal Publisher: The African Field Epidemiology Network ISSN (Electronic): 1937-8688 Publication date (Electronic [scienceopen.com]

Epidemiology of type 2 diabetes: Indian scenario. Indian J Med Res 2007;125:217-30. [ PUBMED ] 12. Wild S, Roglic G, Green A, Sicree R, King H. Global prevalence of diabetes: Estimates for the year 2000 and projections for 2030. [ijo.in]

A previously unreported potential pathophysiologic injury mechanism is theorized based upon anatomical structure and mode of injury. [ncbi.nlm.nih.gov]

The possibility of multifactorial pathophysiology therefore seems likely. [doi.org]

Sixth nerve palsy causes the eyes to deviate inward (see: Pathophysiology of strabismus). [en.wikipedia.org]

Prompt diagnosis and management before intracranial extension can prevent devastating complications. [ncbi.nlm.nih.gov]

Occlusion therapy is necessary to alleviate diplopia and prevent amblyopia in children younger than 7 years. [ojoonline.org]

The disorder prevents some of the muscles that control eye movement from working properly. Affected people cannot turn the eye outwards toward the ear. Other signs and symptoms may include double vision, headaches, and pain around the eye. [rarediseases.info.nih.gov]

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3. Patel SV, Mutyala S, Leske DA, Hodge DO, Holmes JM. Incidence, associations, and evaluation of sixth nerve palsy using a population-based method. Ophthalmology. 2004;111(2):369-375.
4. Reyes KB, Lee HY, Ng I, Goh KY. Abducens (sixth) nerve palsy presenting as a rare case of isolated brainstem metastasis from a primary breast carcinoma. Singapore Med J. 2011;52(11):e220-222.
5. Porter RS, Kaplan JL. Merck Manual of Diagnosis and Therapy. 19th Edition. Merck Sharp & Dohme Corp. Whitehouse Station, N.J; 2011.
6. Nair AG, Ambika S, Noronha VO, Gandhi RA. The diagnostic yield of neuroimaging in sixth nerve palsy - Sankara Nethralaya Abducens Palsy Study (SNAPS): Report 1. Indian J Ophthalmol. 2014;62(10):1008-1012.
7. Reid JE, Reem RE, Aylward SC, Rogers DL. Sixth Nerve Palsy in Paediatric Intracranial Hypertension. Neuro-Ophthalmology. 2016;40(1):23-27.