Periorbital Cellulitis Symptoms and Causes

Introduction

Periorbital cellulitis (Preseptal Cellulitis) is a type of soft tissue infection that occurs at the eyelid and surrounding skin. In periorbital cellulitis, the skin region anterior to the orbital septum is affected while the eyeball is spared. Compared to adults, children are more likely to develop periorbital cellulitis especially those who are younger than 10 years. According to the College of Optometrists,¹ the incidence of occurrence is 1.6 per 100,000 to 6 per 100,000 in children under the age of 18 years, and 0.6 per 100,000 to 2.4 per 100,000 in adults. Nevertheless, it still can happen to anyone regardless of age and if left untreated, it may lead to serious complications. Therefore, it is essential that we look out for symptoms of periorbital cellulitis and know what causes periorbital cellulitis. In order to understand it better, a brief explanation about the anatomy of the orbit and its surrounding structure so that we know why the infection happens and spreads. The orbit is lined by periosteum (a type of dense and fibrous membrane that covers the outer surface of the bone) and surrounding it are the paranasal sinuses which consist of the frontal sinus superiorly, ethmoid sinus medially, maxillary sinus inferiorly. Due to its surrounding structures, an infection of the sinus (especially ethmoid sinus) can progress rapidly due to its close proximity. Furthermore, the lamina papyracea(a thin sheet of osseous structure) serves as the only structure that segregates the ethmoid sinus and orbit. This lamina is incredibly thin and filled with multiple perforations and fenestrations to allow passage of blood supplies and nerves. Infection of the sinuses can spread easily to the surrounding region.²

Symptoms

In periorbital cellulitis, the complaints are commonly unilateral and present with symptoms such as swelling, oedema and redness of the eyelid. Because it is a superficial infection and the inflammation that occurs is anterior to periocular tissue, the extraocular muscles are spared. Hence, the patient would not complain of difficulties moving the eye. However, they may complain of difficulty opening the eyelid due to the swelling. The absence of fever usually points towards periorbital cellulitis. Despite this, there are cases of periorbital cellulitis associated with fever. Hence the presence of fever does not rule out periorbital cellulitis. Upon examination, the affected area can be extremely painful or tender to touch.³ Unlike orbital cellulitis which can affect the vision, those who suffer from periorbital cellulitis rarely complain of vision problems.  If symptoms such as vision changes (double or blurry vision ), significant pain upon moving the eyeball and proptosis (eyeball prompting forward) may point towards orbital cellulitis which is another type of eye infection that involves the orbital contents such as the fat and extraocular muscles.^4,5

Causes and risk factors

Periorbital cellulitis can be caused by a variety of reasons with the most common cause being bacterial infections. Species such as Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus pyogenes are known to cause most of the cases. In some cases, fungi can cause periorbital cellulitis as well.⁶ Another reason for it can be because of the spread of nearby infections. Sinus infections like sinusitis can spread to the surrounding region and cause periorbital cellulitis to occur. That’s why cases of it can commonly be seen in spring and winter months⁷ which are seasons where sinus infections are more likely to happen. Besides that, skin injuries and insect bites around the eye may cause infection of the skin leading to periorbital cellulitis. Certain groups of individuals are more prone to develop periorbital cellulitis. Firstly, children are more susceptible to it compared with adults due to their underdeveloped immune system. Furthermore, Individuals with weakened immune systems are unable to fight infections efficiently hence making them more likely to suffer from infections. Recent eye surgery and trauma also increase the risk of developing periorbital cellulitis as there is always a risk of complications when surgical interventions are done. Individuals who suffer from chronic sinusitis are also more likely to suffer from periorbital cellulitis as sinusitis can spread towards the surrounding region and it is one of the common reasons for periorbital cellulitis. Individuals who suffer from chronic illnesses such as diabetes are more prone to infection due to the disruption of the immune system in those individuals as Innate and adaptive immunity are affected along with cytokine signalling. Moreover, vascular complications in diabetes can occur, causing poor blood flow to sites of infection leading to secondary infections and more complications.⁸

Diagnosis 

Periorbital cellulitis is usually a clinical diagnosis. However, a few tests could be done to improve diagnostic accuracy as well as monitor disease progression or response to treatment. An eye examination is done in the clinic to make sure that there are no issues with the vision. Visual acuity and visual field can be checked to ensure that vision is intact. In cases where there is significant oedema, imaging tests such as CT or an MRI can be done. This is useful as sometimes the eyelid oedema is so severe that it precludes eye examination, thus making it difficult to differentiate periorbital and orbital cellulitis.⁹ Furthermore, a complete blood count could be ordered to see if there is an abnormality in leucocytes which may signify infection. A blood culture can be ordered if necessary to find out the causative organism so that it can be managed accordingly. Some other eye conditions may present with symptoms that are similar to periorbital cellulitis. Therefore, a careful examination of the periocular region is needed to rule out inflammatory or allergic causes namely blepharitis, conjunctivitis and dermatitis. 

Complications and prognosis

Complications in periorbital cellulitis are rare and the prognosis is excellent if it is diagnosed and managed quickly. However, the outcome is based on a few factors such as age, severity of disease and health status. Even with appropriate treatment, complications can still occur in periorbital cellulitis. Unresolved periorbital cellulitis can extend into the orbit contents and surrounding structures causing orbital cellulitis, abscesses and cavernous sinus thrombosis. The infection can spread to other parts of the body as well, especially the central nervous system due to its close proximity. Complications such as meningitis and brain abscesses can happen and it is crucial that we make sure that we look out for nervous system involvement when an examination is done. Necrotising fasciitis is another concerning complication. It is caused by β-hemolytic Streptococcus and presents as a type of rapidly progressive cellulitis. The skin of affected individuals is seen with poorly demarcated borders and violaceous discolouration. If the condition is not managed in time it can lead to necrosis and toxic shock syndrome which may lead to organ failure and other fatal complications. 

Summary

Periorbital cellulitis is a type of soft tissue infection of the eyelids and surrounding region with children being the most likely to suffer from it. They typically manifest as eyelid swelling and redness without changes in vision and usually affect one eye. The most common cause of periorbital cellulitis is bacterial infection but sinus infection and trauma or injury to the eye can cause it to happen as well. It is usually a clinical diagnosis but testing and imaging can be done to monitor for any orbital or brain involvement. It is crucial to seek treatment as soon as possible. If left untreated it may cause severe complications such as abscesses and can damage the nervous system due to its close proximity to the brain. In some cases, it may develop into orbital cellulitis which may affect vision. The prognosis is based on early recognition of symptoms and treatment. Hence, if we recognise the symptoms early on intervention could be done as soon as possible drastically improving the outcome.