Orbital Infections — MCQs
An 18-month-old child presents with cellulitis of the leg and SpO2 of 88%. There is no prior history of hospitalization or illness. What is the most probable organism?
A man presents 6 hrs after head injury complaining of mild proptosis and scleral hyperemia:
The patient presents with unilateral proptosis and bilateral abducent nerve palsy. What is the most likely cause?
A 19-year-old young girl with a previous history of repeated pain over the medial canthus and chronic use of nasal decongestants presented with an abrupt onset of fever, chills, and rigor, diplopia on lateral gaze, moderate proptosis, and chemosis. On examination, the optic disc is congested. What is the most likely diagnosis?
Organism involved in cellulitis is:
A 65-year-old diabetic man presents with black necrotic tissue on his palate. What is the most likely causative organism?
All are causes of proptosis except:
Enophthalmos can be caused by all of the following EXCEPT:
Blow out fracture of orbit commonly involves:-
A 25 -year-old lady with past history of seeing colored haloes was watching a movie in a theater when she started having right eye pain. She started feeling nauseous and had to leave the movie midway due to vomiting. On examination she is found to have ciliary and conjunctival congestion and the pupil is vertically oval. The picture of the eye is given below. All are true about the condition shown except:
Orbital Infections Indian Medical PG Practice Questions and MCQs
Question 1: An 18-month-old child presents with cellulitis of the leg and SpO2 of 88%. There is no prior history of hospitalization or illness. What is the most probable organism?
- A. MRSA
- B. Streptococcus pyogenes
- C. Streptococcus pneumoniae (Correct Answer)
- D. All of the options
Explanation: ***Streptococcus pneumoniae*** - **Streptococcus pneumoniae** is the most probable organism given the clinical presentation of cellulitis with **hypoxia (SpO2 88%)** in a previously healthy 18-month-old child. - The key finding is the **low oxygen saturation**, which suggests **concurrent pneumonia or bacteremia** with respiratory involvement, not just isolated skin infection. - **Pneumococcal bacteremia** in young children commonly presents with distant site infections (including cellulitis) along with primary respiratory manifestations—explaining both the leg cellulitis and the desaturation. - This age group (18 months) is particularly susceptible to invasive pneumococcal disease, especially if not fully vaccinated or if vaccine coverage is incomplete. *Streptococcus pyogenes* - **Streptococcus pyogenes** (Group A Streptococcus) is indeed a common cause of **cellulitis** in children and can cause rapid local spread. - However, it typically does NOT cause significant **hypoxia** unless there is extensive tissue destruction (necrotizing fasciitis) or toxic shock syndrome, which would present with additional features like severe toxicity, shock, or multi-organ involvement. - The isolated finding of SpO2 88% with cellulitis is more consistent with a pathogen that commonly affects both skin and respiratory system simultaneously. *MRSA* - **MRSA (Methicillin-resistant Staphylococcus aureus)** is a significant cause of skin and soft tissue infections, particularly abscesses and furuncles. - While MRSA can cause severe cellulitis, the **hypoxia** would be unusual unless there is concurrent necrotizing pneumonia or sepsis with ARDS, which is less common in an otherwise healthy child with no prior hospitalization. - The absence of prior healthcare exposure makes community-acquired MRSA possible, but it doesn't explain the respiratory compromise as well as pneumococcus does. *All of the options* - While multiple organisms can cause pediatric cellulitis, the **specific clinical picture** with significant hypoxia points most strongly to **Streptococcus pneumoniae**. - The combination of cellulitis + respiratory compromise is characteristic of pneumococcal bacteremia in this age group, making it the MOST probable single organism.
Question 2: A man presents 6 hrs after head injury complaining of mild proptosis and scleral hyperemia:
- A. Caroticocavernous fistula
- B. Retro-orbital hematoma (Correct Answer)
- C. Pneumo-orbit
- D. Orbital cellulitis
Explanation: ***Retro-orbital hematoma*** - The sudden onset of **proptosis** and **scleral hyperemia** within hours of a head injury is highly suggestive of bleeding behind the eye. - A **retro-orbital hematoma** causes increased orbital pressure, leading to the forward displacement of the eyeball (proptosis) and conjunctival injection (scleral hyperemia). *Caroticocavernous fistula* - This condition involves an abnormal communication between the carotid artery and the cavernous sinus, typically presenting with a **pulsatile proptosis** and a **bruit** over the eye. - While it can cause proptosis and hyperemia, its onset is usually not as acute as 6 hours post-trauma without being a direct major vessel injury in a recent trauma. *Pneumo-orbit* - A pneumo-orbit involves **air entering the orbit**, often following trauma that fractures an orbital wall communicating with a paranasal sinus. - Symptoms include **periorbital crepitus** and exophthalmos, but scleral hyperemia is not a primary or dominant feature. *Orbital cellulitis* - Orbital cellulitis is an **infection of the orbital tissues**, usually presenting with proptosis, ophthalmoplegia, pain, and fever. - This is an infectious process and would typically take longer than 6 hours to develop to such an extent after an acute trauma without an open wound or obvious contamination.
Question 3: The patient presents with unilateral proptosis and bilateral abducent nerve palsy. What is the most likely cause?
- A. Cavernous sinus pathology (Correct Answer)
- B. Orbital cellulitis
- C. Orbital pseudotumor
- D. Orbital lymphoma
Explanation: The patient presents with unilateral proptosis and bilateral abducent nerve palsy. What is the most likely cause? ***Cavernous sinus pathology*** - **Unilateral proptosis** combined with **bilateral abducens nerve palsy** is a classic presentation consistent with cavernous sinus involvement, as the abducens nerves (CN VI) pass through both cavernous sinuses and are vulnerable to pathology there. [1] - The cavernous sinus contains multiple cranial nerves (**III, IV, V1, V2, VI**) and the internal carotid artery, making it a critical anatomical location where lesions can cause complex neurological deficits affecting orbital structures and eye movements. [1] *Orbital cellulitis* - Typically presents with **unilateral proptosis**, pain, eyelid swelling, and fever, often following a sinus infection. - It primarily affects the **orbital contents anterior to the orbital septum** and would not explain bilateral abducens nerve palsy. *Orbital pseudotumor* - Characterized by **unilateral proptosis**, pain, and diplopia due to idiopathic inflammation of orbital tissues. - While it can cause ophthalmoplegia, **bilateral abducens nerve palsy** is not a typical presentation for a condition usually confined to one orbit. *Orbital lymphoma* - Presents with **painless, slowly progressive unilateral proptosis** or an orbital mass. - While it can cause compressive symptoms, **bilateral abducens nerve palsy** is an atypical presentation as the disease usually remains confined to a single orbit.
Question 4: A 19-year-old young girl with a previous history of repeated pain over the medial canthus and chronic use of nasal decongestants presented with an abrupt onset of fever, chills, and rigor, diplopia on lateral gaze, moderate proptosis, and chemosis. On examination, the optic disc is congested. What is the most likely diagnosis?
- A. Cavernous sinus thrombosis (Correct Answer)
- B. Orbital inflammation
- C. Acute sinusitis
- D. Optic nerve compression
Explanation: **Cavernous sinus thrombosis** - The abrupt onset of **fever, chills, rigor, diplopia on lateral gaze, moderate proptosis, and chemosis, along with a congested optic disc**, points towards inflammation and thrombosis within the cavernous sinus. - A history of recurrent pain over the **medial canthus** (suggesting infection near the nose/eyes) and chronic use of **nasal decongestants** (potentially obstructing venous drainage or causing mucosal changes) further increases the suspicion for cavernous sinus thrombosis originating from orbital or sinonasal infections. *Orbital inflammation* - While orbital inflammation can present with **proptosis, chemosis, and optic disc congestion**, the presence of **diplopia on lateral gaze (suggesting oculomotor nerve involvement)** and systemic symptoms like **fever, chills, and rigor** strongly indicates a more widespread and severe process beyond simple inflammation, such as thrombosis. - Orbital inflammation typically lacks the characteristic severe systemic toxicity and specific cranial nerve palsies associated with cavernous sinus thrombosis. *Acute sinusitis* - **Acute sinusitis** can present with fever and localized pain, but it does not typically cause **diplopia on lateral gaze, significant proptosis, chemosis, or optic disc congestion**. - The symptoms described are much more severe and involve structures beyond the paranasal sinuses. *Optic nerve compression* - **Optic nerve compression** would primarily cause visual disturbances, such as **vision loss or visual field defects**, and potentially optic disc edema. [1] - It would not explain the prominent **proptosis, chemosis, diplopia on lateral gaze**, or the significant systemic symptoms like **fever, chills, and rigor**.
Question 5: Organism involved in cellulitis is:
- A. S. mutans
- B. Klebsiella
- C. Pneumococci
- D. S. pyogenes (Correct Answer)
Explanation: ***Strept. pyogenes*** - *Streptococcus pyogenes* (Group A Streptococcus) is a common cause of **cellulitis**, an acute bacterial infection of the deep dermis and subcutaneous tissue. - It often spreads rapidly and can lead to systemic symptoms if untreated. *Strept. mutans* - *Streptococcus mutans* is primarily associated with **dental caries** (tooth decay) and is a significant component of oral biofilm. - It is not a common cause of cellulitis in typical settings. *Pneumococci* - **Pneumococci** (*Streptococcus pneumoniae*) are most commonly known for causing **pneumonia**, otitis media, and meningitis. - While they can cause invasive infections, they are not a primary cause of routine cellulitis. *Klebsiella* - *Klebsiella* species are common causes of **nosocomial infections**, particularly urinary tract infections, pneumonia, and bloodstream infections. - They can cause cellulitis, especially in immunocompromised individuals or those with specific risk factors, but *S. pyogenes* is more common in general cellulitis cases.
Question 6: A 65-year-old diabetic man presents with black necrotic tissue on his palate. What is the most likely causative organism?
- A. Cryptococcus neoformans
- B. Candida albicans
- C. Mucor species (Correct Answer)
- D. Aspergillus fumigatus
Explanation: ***Mucor species*** - The presence of **black necrotic tissue** on the palate in a diabetic patient is highly suggestive of **mucormycosis**, an aggressive fungal infection caused by *Mucor* species. - **Diabetes mellitus**, particularly with ketoacidosis, is a major risk factor for mucormycosis due to impaired phagocytic function and increased iron availability. *Cryptococcus neoformans* - This fungus is primarily associated with **cryptococcal meningitis** or pneumonia, especially in immunocompromised individuals. - It does not typically cause **black necrotic lesions** on the palate. *Candida albicans* - While *Candida albicans* can cause oral infections (**thrush**), these typically present as white, creamy patches that can be scraped off, not black necrotic tissue. - Oral candidiasis is common in diabetics but does not usually involve tissue necrosis. *Aspergillus fumigatus* - *Aspergillus* species can cause invasive infections, particularly in immunocompromised patients, often affecting the lungs or sinuses. - While it can cause **necrotic lesions**, the characteristic rapid progression and specific presentation in the palate of a diabetic with black necrotic tissue points more strongly towards *Mucor*.
Question 7: All are causes of proptosis except:
- A. Orbital cellulitis
- B. Orbital tumor
- C. Retinal detachment (Correct Answer)
- D. Graves' disease
Explanation: ***Retinal detachment*** - **Retinal detachment** is a condition where the retina separates from the underlying supportive tissue and does not cause proptosis. - Its primary symptoms include **flashes of light**, **floaters**, and a **curtain-like shadow** in the visual field. *Orbital cellulitis* - **Orbital cellulitis** is an infection of the fat and muscles around the eye, leading to inflammation and swelling. - This swelling can push the eye forward, causing **proptosis**. *Orbital tumor* - An **orbital tumor** is a mass growing within the orbit (eye socket), which occupies space and displaces the eyeball. - This displacement typically results in **proptosis**, often unilateral and progressive. *Graves' disease* - **Graves' disease** (or Graves' ophthalmopathy) involves inflammation and swelling of the extraocular muscles and orbital fat due to autoimmune processes. - This increased volume within the orbit directly causes **proptosis** and is often bilateral.
Question 8: Enophthalmos can be caused by all of the following EXCEPT:
- A. Orbital floor fracture
- B. Loss of orbital fat
- C. Horner's syndrome (Correct Answer)
- D. Cicatricial changes
Explanation: ***Horner's syndrome*** - **Horner's syndrome** is characterized by **ptosis**, **miosis**, and **anhidrosis** on the affected side. - While it can manifest with a mild degree of **apparent enophthalmos**, this is primarily due to the **ptosis creating an illusion** of globe retraction and **not true enophthalmos**. - It is caused by disruption of the **sympathetic nervous supply**, not by actual posterior displacement of the globe. *Cicatricial changes* - **Cicatricial changes** (scarring) within the orbit can cause **traction on the globe**, pulling it inward and resulting in **true enophthalmos**. - This scarring can occur following **trauma**, **inflammation**, or **surgery** affecting the orbital tissues. *Orbital floor fracture* - An **orbital floor fracture** typically leads to **enophthalmos** due to **herniation of orbital contents** (fat, muscle) into the maxillary sinus. - This involves a **structural defect** with increased orbital volume and loss of support for the globe. *Loss of orbital fat* - **Loss of orbital fat**, often seen in conditions like **Romberg's disease**, severe dehydration, or aging, causes the globe to sink backward. - This is due to a **reduction in volume supporting the globe**, resulting in **true enophthalmos**.
Question 9: Blow out fracture of orbit commonly involves:-
- A. Medial wall is involved first as it is the thinnest
- B. Floor is involved first (Correct Answer)
- C. Roof is involved first as it bears the maximum impact
- D. The patient is not able to look up due to inferior rectus entrapment
Explanation: ***Floor is involved first*** - The **orbital floor** (composed mainly of the maxillary bone and portions of the palatine and zygomatic bones) is the most common site for a **blowout fracture** due to its relative weakness. - Trauma to the globe increases **intraorbital pressure**, causing the weakest part of the orbit, which is commonly the floor, to fracture and displace fragments into the maxillary sinus. *Medial wall is involved first as it is the thinnest* - While the **medial wall** (primarily the lacrimal bone and the lamina papyracea of the ethmoid bone) is indeed the **thinnest** portion of the orbit, it is structurally supported by the ethmoid air cells, making it less prone to fracture from direct globe impact compared to the floor. - Fractures of the medial wall can occur but are less common as the primary site of injury than the orbital floor. *The patient is not able to look up due to inferior rectus entrapment* - While **inferior rectus muscle** entrapment in orbital floor fractures does cause restricted upward gaze, this is a **complication** of the fracture, not what the fracture "commonly involves" anatomically. - The question asks which **anatomical structure** is commonly involved, not the clinical presentation. - Inferior rectus entrapment occurs in blowout fractures but doesn't answer which orbital wall is most commonly fractured. *Roof is involved first as it bears the maximum impact* - The **orbital roof** (formed by the frontal bone) is the strongest part of the orbit and rarely fractures from globe impact alone; it typically requires high-energy trauma to the forehead. - If the roof were involved, it would likely be due to direct impact to the supraorbital region, not from compression of the globe which usually affects the floor or medial wall.
Question 10: A 25 -year-old lady with past history of seeing colored haloes was watching a movie in a theater when she started having right eye pain. She started feeling nauseous and had to leave the movie midway due to vomiting. On examination she is found to have ciliary and conjunctival congestion and the pupil is vertically oval. The picture of the eye is given below. All are true about the condition shown except:
- A. Loss of iris pattern
- B. Steamy insensitive cornea
- C. Absent reaction to light and accommodation
- D. Present PL (Correct Answer)
Explanation: ***Present PL (Perception of Light)*** - In **acute angle-closure glaucoma (AACG)**, visual acuity is typically severely reduced due to corneal edema and elevated intraocular pressure, but **perception of light (PL) is usually preserved** in acute presentations. - While vision may be reduced to counting fingers or hand movements, **complete loss of light perception is uncommon** unless there is severe, prolonged attack with irreversible optic nerve damage. - All other features listed (loss of iris pattern, steamy cornea, absent pupillary reactions) are **consistently present** in AACG, whereas PL can be variable but is typically **present initially**. - This makes "Present PL" the **correct answer** as it is the statement that is **NOT always/universally true** - though PL is often present, the question implies it as a definitive feature when it's actually variable. *Loss of iris pattern* - This is a **consistent finding** in AACG during an acute attack. - The iris becomes **edematous** due to elevated intraocular pressure (often >40 mmHg), which obscures the normal radial folds and crypts. - The iris appears dull, muddy, and featureless - a key diagnostic sign. *Steamy insensitive cornea* - The markedly elevated intraocular pressure causes **corneal epithelial and stromal edema**. - This produces a **hazy or "steamy" appearance** that interferes with visualization of anterior chamber structures. - Corneal sensation may be reduced due to epithelial edema and ischemia. *Absent reaction to light and accommodation* - The pupil in AACG is characteristically **fixed and mid-dilated (4-6 mm)**, often vertically oval as described. - **Complete absence of pupillary light reflex** (both direct and consensual) occurs due to iris sphincter ischemia. - **No accommodation response** due to the fixed, dilated pupil and compromised iris function.
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