Foreign body of organic origin, in the orbit

Clinical History

A 1-year-old child was admitted from the outpatient department because of irritability, with concomitant erythema, oedema and pain of the right eye. During the clinical examination, a slight exopthalmus was determined together with the inability of internal and external rotation of the ocular bulb.

Imaging Findings

The CT examination showed free air inside the right orbit, exopthalmus and inflammatory changes of the periorbital fat (Fig. 1) under the ocular bulb. The extraocular muscles were not affected and the ocular bulb was intact (Fig. 2, 3). Due to the clinical picture and inability of a clear clinical history together with the CT images, a first diagnosis of orbital cellulitis and a possible abscess formation was speculated.
Α month later the patient was re-admitted due to reappearance of the initial clinical symptoms. A new CT examination showed improvement of the inflammatory signs of the eye (Fig. 4a, b). A more detailed study was instigated and the presence of a foreign body alongside the ocular bulb extending up to the supratemporal fossa was suspected. It had characteristic high densities as that of the soft tissue. The third CT, after 15 days of treatment, clearly presented a foreign body as a well defined solid mass of soft tissue density with a specific longitudinal shape (Fig. 5a, b, c)

Discussion

Foreign body detection especially of organic origin can be very difficult, even more so when children are involved without any visible signs of point of entry [1]. Even slight injuries are overlooked most of the times. Wood as an organic matter is a very good substrate for the development of bacteria, eventually leading to inflammation with abscess formation [2]. Simple X-rays are most of the time unable to detect foreign bodies. CT has the ability to differentiate between matters depending on its consistency: solid, porous, green, or dehydrated. The most common foreign bodies found are metallic objects and glass [3]. Sometimes these objects penetrate the orbit and are found in neighbouring areas such as the paranasal sinuses and nasal cavity or inside the cranium itself [4, 5]. Findings vary from simple lacerations, erythema and oedema localised at the point of entry to functional disturbance of the orbital muscles and injury to the ocular bulb itself [5] and free orbital air. Rarely, complications such as cellulitis and abscess formation have also been described. The intracranial complications such as CSF leakage meningitis and abscess formation have a worse outcome (48% abscess formation, 25 % mortality rate) [5]. Foreign bodies that don’t have high densities share characteristics usually similar to air bubbles or bony parts [5] but in the case of subacute or chronic trauma present in the form of a mass caused by granulomatous reactions. In these cases MRI can often provide the solution. Wooden object densities depend on its water content which varies from very low to very high [5]. Foreign bodies are great mimickers. Many times they can be confused with fatty tissue [6], or free air which can occasionally be found within the bulb [5, 7]. It has been reported that HU units of wood can increase with time [8, 9]. In the beginning, if it is porous, it mimics air. In this phase the presence of air inside the orbit could be attributed to a fracture of the paranasal sinuses, trauma or an organic foreign body. In the subacute phase, wood presents as an intermediate density and can be very difficult to differentiate between surrounding tissues. In chronic phases densities become greater than the densities of the orbital muscles [5]. In addition it could be combined with an inflammatory response surrounding the foreign body which is seen as a homogenous mass. The changes in density are related to the gradual replacement of air with fluid. Another factor playing an important role of the density of the organic matter in different stages is the structure itself [5].

Differential Diagnosis List

Final Diagnosis

Cellulitis caused by intraorbital foreign body

URL:	https://www.eurorad.org/case/10972
DOI:	10.1594/EURORAD/CASE.10972
ISSN:	1563-4086