Nasal cavity and paranasal sinuses US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Nasal cavity and paranasal sinuses. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Nasal cavity and paranasal sinuses US Medical PG Question 1: A 17-year-old boy presents to his primary care physician for eye pain. The patient states that it has been going on for the past 3 days and has been steadily worsening. He recently suffered a superior orbital fracture secondary to playing football without a helmet that required no treatment other than to refrain from contact sports. The patient's past medical history is non-contributory, and his vitals are within normal limits. Physical exam demonstrates pain and swelling inferior to the patient's eye near the lacrimal duct. When pressure is applied to the area expressible pus is noted. Cranial nerves II-XII are grossly intact. Which of the following is the most likely diagnosis?
- A. Orbital cellulitis
- B. Hordeolum
- C. Periorbital cellulitis
- D. Dacrocystitis (Correct Answer)
- E. Abscess
Nasal cavity and paranasal sinuses Explanation: ***Dacrocystitis***
- The presentation of **eye pain**, swelling inferior to the eye near the **lacrimal duct**, and the presence of **expressible pus** upon pressure strongly indicates dacryocystitis, which is an infection of the **lacrimal sac**.
- The history of a recent orbital fracture, while not directly causing the infection, could predispose the area to inflammation or obstruction leading to infection.
*Orbital cellulitis*
- This condition would present with more severe symptoms, including **pain with eye movement**, **proptosis** (exophthalmos), **ophthalmoplegia**, and vision changes, which are not described.
- Infection is **posterior to the orbital septum**, often extending from sinusitis, and is a medical emergency.
*Hordeolum*
- A hordeolum (stye) is an acute infection of the glands of the eyelid, presenting as a **tender, red bump on the eyelid margin**, not inferior to the eye near the lacrimal duct.
- It typically involves the **sebaceous glands** (external hordeolum) or **Meibomian glands** (internal hordeolum).
*Periorbital cellulitis*
- Also known as preseptal cellulitis, this involves infection of the tissues **anterior to the orbital septum**, causing eyelid swelling and redness but **without pain on eye movement**, proptosis, or vision changes.
- Unlike dacryocystitis, the infection is more diffuse around the periorbital area and not specifically focused on the lacrimal sac with expressible pus.
*Abscess*
- While dacryocystitis can lead to an abscess of the lacrimal sac, "abscess" alone is a general term. **Dacryocystitis** specifically describes the infection and inflammation of the lacrimal sac, which is the most precise diagnosis here given the location and expressible pus.
- An abscess typically implies a **localized collection of pus** within a tissue, but dacryocystitis defines the primary affected structure.
Nasal cavity and paranasal sinuses US Medical PG Question 2: A 25-year-old woman presents to the physician with a complaint of several episodes of headaches in the past 4 weeks that are affecting her school performance. These episodes are getting progressively worse, and over-the-counter medications do not seem to help. She also mentions having to raise her head each time to look at the board while taking notes; she cannot simply glance up with just her eyes. She has no significant past medical or family history and was otherwise well prior to this visit. Physical examination shows an upward gaze palsy and convergence-retraction nystagmus. What structure is most likely to be affected in this patient?
- A. Aqueduct of Sylvius
- B. Inferior colliculi
- C. 3rd ventricle
- D. Tegmentum
- E. Corpora quadrigemina (Correct Answer)
Nasal cavity and paranasal sinuses Explanation: ***Corpora quadrigemina***
- The patient presents with classic **Parinaud syndrome** (dorsal midbrain syndrome), characterized by **upward gaze palsy** and **convergence-retraction nystagmus**.
- These specific oculomotor signs result from direct damage to the **superior colliculi** and **pretectal area**, which are anatomical components of the **corpora quadrigemina** in the tectal region of the midbrain.
- The superior colliculi control vertical gaze, and the pretectal area coordinates pupillary reflexes and convergence movements. Compression or infiltration of this region (commonly by pineal tumors) produces the characteristic eye movement abnormalities.
- Progressive headaches indicate increased intracranial pressure, often from associated **aqueduct obstruction** causing hydrocephalus, which in turn compresses the tectal structures.
*Aqueduct of Sylvius*
- While obstruction of the aqueduct of Sylvius commonly **causes** Parinaud syndrome by leading to hydrocephalus and mass effect, the aqueduct itself is a CSF pathway and does not directly produce the eye movement abnormalities.
- The question asks which structure is "**affected**" - the affected structure producing these specific symptoms is the tectal region (corpora quadrigemina), not the obstructed aqueduct.
- This is an important distinction: the aqueduct is obstructed, but the corpora quadrigemina is compressed/affected.
*Inferior colliculi*
- The inferior colliculi are part of the corpora quadrigemina but serve the **auditory pathway**, not visual or oculomotor functions.
- Isolated lesions here would cause hearing deficits, not upward gaze palsy or convergence-retraction nystagmus.
*3rd ventricle*
- Lesions obstructing the third ventricle can cause hydrocephalus and headaches but do not directly affect the midbrain tectum unless they extend posteriorly.
- Third ventricular masses more commonly produce **endocrine disturbances** (hypothalamic-pituitary axis dysfunction) rather than the specific dorsal midbrain syndrome seen here.
*Tegmentum*
- The tegmentum is the ventral portion of the midbrain containing the **red nucleus**, **substantia nigra**, and **cranial nerve nuclei (III, IV)**.
- Tegmental lesions produce different oculomotor deficits (e.g., internuclear ophthalmoplegia, third nerve palsy) and movement disorders, not the dorsal midbrain syndrome pattern of Parinaud.
Nasal cavity and paranasal sinuses US Medical PG Question 3: A 47-year-old woman presents to the emergency department with a fever and a headache. Her symptoms started yesterday and have rapidly progressed. Initially, she was experiencing just a fever and a headache which she was treating with acetaminophen. It rapidly progressed to blurry vision, chills, nausea, and vomiting. The patient has a past medical history of diabetes and hypertension and she is currently taking insulin, metformin, lisinopril, and oral contraceptive pills. Her temperature is 104°F (40.0°C), blood pressure is 157/93 mmHg, pulse is 120/min, respirations are 15/min, and oxygen saturation is 98% on room air. Upon further inspection, the patient also demonstrates exophthalmos in the affected eye. The patient's extraocular movements are notably decreased in the affected eye with reduced vertical and horizontal gaze. The patient also demonstrates decreased sensation near the affected eye in the distribution of V1 and V2. While the patient is in the department waiting for a CT scan, she becomes lethargic and acutely altered. Which of the following is the most likely diagnosis?
- A. Acute closed angle glaucoma
- B. Cavernous sinus thrombosis (Correct Answer)
- C. Brain abscess
- D. Periorbital cellulitis
- E. Intracranial hemorrhage
Nasal cavity and paranasal sinuses Explanation: ***Cavernous sinus thrombosis***
- The rapid progression of symptoms, **exophthalmos**, decreased extraocular movements (involving cranial nerves III, IV, and VI that pass through the cavernous sinus), and V1/V2 sensory deficits (trigeminal nerve branches) are classic signs of **cavernous sinus thrombosis**. The patient's acute alteration and lethargy point to CNS involvement.
- The patient's oral contraceptive use is a risk factor for **thrombosis**, and her diabetic and hypertensive status may contribute to her vulnerability to infections, which can lead to cavernous sinus thrombosis.
*Acute closed angle glaucoma*
- Acute closed-angle glaucoma typically presents with sudden, severe eye pain, blurred vision, and halos, often without systemic symptoms like fever or rapid progression to altered mental status.
- While it causes blurry vision, it does not typically cause **exophthalmos**, multiple extraocular muscle palsies, or deficits in V1/V2 sensation.
*Brain abscess*
- A brain abscess can cause fever, headache, and altered mental status, but it less commonly presents with the specific combination of **exophthalmos**, multiple cranial nerve palsies affecting eye movement, and V1/V2 sensory deficits.
- It would typically cause focal neurological deficits related to the specific brain region affected, rather than a constellation of orbital and systemic symptoms like this.
*Periorbital cellulitis*
- Periorbital cellulitis causes eyelid swelling, redness, and pain, and can be associated with fever, but it typically does not cause **exophthalmos**, decreased extraocular movements, or sensory deficits in the V1/V2 distribution as seen in this patient.
- Infection is limited to tissues anterior to the orbital septum and generally resolves with antibiotics without progression to severe neurological symptoms.
*Intracranial hemorrhage*
- Intracranial hemorrhage can cause sudden headache, altered mental status, and focal neurological deficits, but it rarely presents with **fever**, **exophthalmos**, or the specific cranial nerve palsies described without other clear signs of a stroke (e.g., sudden weakness or speech changes).
- The presence of fever and the constellation of orbital signs make hemorrhage less likely as the primary diagnosis.
Nasal cavity and paranasal sinuses US Medical PG Question 4: A 72-year-old man is brought to the physician for the evaluation of severe nosebleeds and two episodes of bloody vomit over the past 40 minutes. He reports that he has had recurrent nosebleeds almost daily for the last 3 weeks. The nosebleeds last between 30 and 40 minutes. He appears pale. His temperature is 36.5°C (97.7°F), pulse is 95/min, and blood pressure is 110/70 mm Hg. Examination of the nose with a speculum does not show an anterior bleeding source. The upper body of this patient is elevated and his head is bent forward. Cold packs are applied and the nose is pinched at the nostrils for 5–10 minutes. Topical phenylephrine is administered. Despite all measures, the nosebleed continues. Anterior and posterior nasal packing is placed, but bleeding persists. Which of the following is the most appropriate next step in management?
- A. Endoscopic ligation of the anterior ethmoidal artery
- B. Endoscopic ligation of the greater palatine artery
- C. Endoscopic ligation of the sphenopalatine artery (Correct Answer)
- D. Endoscopic ligation of the posterior ethmoidal artery
- E. Endoscopic ligation of the lesser palatine artery
Nasal cavity and paranasal sinuses Explanation: ***Endoscopic ligation of the sphenopalatine artery***
- The patient presents with **severe, recurrent epistaxis** that is unresponsive to conservative measures, anterior and posterior packing, indicating a **posterior nasal bleed**. The sphenopalatine artery is the primary blood supply to the posterior nasal cavity.
- **Ligation of the sphenopalatine artery** is a highly effective surgical intervention for intractable posterior epistaxis, providing definitive control of bleeding in such cases.
*Endoscopic ligation of the anterior ethmoidal artery*
- The **anterior ethmoidal artery** primarily supplies the superior and anterior nasal septum and lateral nasal wall; ligation would be considered for **anterior superior epistaxis** that is difficult to control.
- Given the failed extensive packing and the severity of bleeding without an obvious anterior source, the bleeding is likely posterior and more widespread than the anterior ethmoidal artery territory.
*Endoscopic ligation of the greater palatine artery*
- The **greater palatine artery** primarily supplies the hard palate; it is not a major source of epistaxis and its ligation would not address the severe, persistent posterior nasal bleeding.
- This artery's contribution to nasal bleeding is minimal, and it is not typically involved in **recurrent severe epistaxis** that requires surgical intervention.
*Endoscopic ligation of the posterior ethmoidal artery*
- The **posterior ethmoidal artery** supplies a small area of the superior posterior nasal septum and lateral wall. While it can contribute to posterior epistaxis, it is a less common source and less significant than the sphenopalatine artery.
- Ligation of the posterior ethmoidal artery alone would be insufficient if the bleeding is primarily from the **sphenopalatine artery territory**, which supplies a much larger area of the posterior nasal cavity.
*Endoscopic ligation of the lesser palatine artery*
- The **lesser palatine artery** supplies the soft palate and tonsillar area; it is not a significant source of epistaxis and its ligation would not be relevant to controlling severe nasal bleeding.
- This artery plays no substantial role in the blood supply of the nasal cavity and would not be targeted for the treatment of **epistaxis**.
Nasal cavity and paranasal sinuses US Medical PG Question 5: A 56-year-old woman presents to the emergency department with a 1-hour history of persistent nasal bleeding. The bleeding started spontaneously. The patient experienced a similar episode last year. Currently, she has hypertension and takes hydrochlorothiazide and losartan. She is anxious. Her blood pressure is 175/88 mm Hg. During the examination, the patient holds a blood-stained gauze against her right nostril. Upon removal of the gauze, blood slowly drips down from her right nostril. Examination of the left nostril reveals no abnormalities. Squeezing the nostrils for 20 minutes fails to control bleeding. Which of the following interventions is the most appropriate next step in the management of this patient?
- A. Nasal oxymetazoline
- B. Anterior nasal packing with topical antibiotics (Correct Answer)
- C. Intravenous infusion of nitroglycerin
- D. Oral captopril
- E. Silver nitrate cauterization of the bleeding vessel
Nasal cavity and paranasal sinuses Explanation: ***Anterior nasal packing with topical antibiotics***
- This is the **most appropriate next step** after failed direct pressure (20 minutes of squeezing the nostrils).
- The standard **stepwise management of anterior epistaxis** proceeds from direct pressure → anterior nasal packing → posterior packing if needed.
- **Anterior nasal packing** provides direct tamponade of the bleeding site and is the definitive treatment when conservative pressure fails.
- **Topical antibiotics** (or antibiotic ointment) are applied to prevent **toxic shock syndrome** and sinusitis, which are rare but serious complications of nasal packing.
*Nasal oxymetazoline*
- **Oxymetazoline** is a topical vasoconstrictor that can help control mild anterior epistaxis.
- It is typically applied **with or before direct pressure**, not after 20 minutes of failed direct pressure.
- While it may be applied before packing, at this point with documented failure of prolonged direct pressure, **packing is the definitive next step**.
- Oxymetazoline alone would be insufficient given the duration and failure of conservative management.
*Silver nitrate cauterization of the bleeding vessel*
- **Cauterization** requires visualization of a discrete bleeding point, which is difficult with active ongoing bleeding.
- It is more appropriate for **recurrent epistaxis** with an identified bleeding vessel or after bleeding is controlled.
- In acute uncontrolled bleeding after failed pressure, **packing takes precedence** over attempting cauterization.
*Intravenous infusion of nitroglycerin*
- **Nitroglycerin** is a vasodilator used for angina, acute coronary syndrome, or hypertensive emergencies with end-organ damage.
- It would **worsen epistaxis** by increasing blood flow and lowering blood pressure.
- The elevated BP (175/88 mm Hg) likely reflects anxiety and pain from epistaxis, not a hypertensive emergency requiring immediate IV treatment.
*Oral captopril*
- While the patient has elevated blood pressure, this does not represent a hypertensive emergency requiring immediate intervention.
- The **priority is controlling the bleeding**, not blood pressure management.
- **ACE inhibitors** like captopril have a slow onset and are inappropriate for acute epistaxis management.
Nasal cavity and paranasal sinuses US Medical PG Question 6: A 45-year-old man is brought to the emergency department after being found down in the middle of the street. Bystanders reported to the police that they had seen the man as he exited a local bar, where he was subsequently assaulted. He sustained severe facial trauma, including multiple lacerations and facial bone fractures. The man is taken to the operating room by the ENT team, who attempted to reconstruct his facial bones with multiple plates and screws. Several days later, he complains of the inability to open his mouth wide or to completely chew his food, both of which he seemed able to do prior to the surgery. Where does the affected nerve exit the skull?
- A. Foramen rotundum
- B. Foramen ovale (Correct Answer)
- C. Jugular foramen
- D. Superior orbital fissure
- E. Inferior orbital fissure
Nasal cavity and paranasal sinuses Explanation: ***Foramen ovale***
- The symptoms of inability to open the mouth wide and difficulty chewing are indicative of damage to the **motor branches of the trigeminal nerve (mandibular nerve)**, which innervates the muscles of mastication.
- The **mandibular nerve (V3)** exits the skull through the **foramen ovale**.
*Foramen rotundum*
- The **foramen rotundum** transmits the **maxillary nerve (V2)**, which is primarily sensory to the midface.
- Damage to this nerve would cause sensory deficits in the cheek, upper lip, and teeth, but not issues with mastication.
*Jugular foramen*
- The **jugular foramen** transmits the **glossopharyngeal (IX)**, **vagus (X)**, and **accessory (XI)** cranial nerves.
- Damage here would lead to problems with swallowing, speech, gag reflex, or shoulder movement, not specifically jaw movement or chewing.
*Superior orbital fissure*
- The **superior orbital fissure** transmits the **oculomotor (III)**, **trochlear (IV)**, **ophthalmic (V1)**, and **abducens (VI)** cranial nerves.
- Damage here would primarily affect eye movements or sensation around the eye and forehead.
*Inferior orbital fissure*
- The **inferior orbital fissure** transmits the **infraorbital nerve** (a branch of V2), **zygomatic nerve**, and other vessels.
- Damage here would result in sensory deficits in the infraorbital region and potentially affect lacrimal gland function, but not mastication.
Nasal cavity and paranasal sinuses US Medical PG Question 7: A 14-year-old boy presents to the emergency department with an intractable nosebleed. Pinching of the nose has failed to stop the bleed. The patient is otherwise healthy and has no history of trauma or hereditary bleeding disorders. His temperature is 98.9°F (37.2°C), blood pressure is 120/64 mmHg, pulse is 85/min, respirations are 12/min, and oxygen saturation is 98% on room air. Physical exam is notable for multiple clots in the nares which, when dislodged, are followed by bleeding. Which of the following locations is the most likely etiology of this patient's symptoms?
- A. Ethmoidal artery
- B. Kiesselbach plexus (Correct Answer)
- C. Sphenopalatine artery
- D. Carotid artery
- E. Greater palatine artery
Nasal cavity and paranasal sinuses Explanation: ***Kiesselbach plexus***
- The **Kiesselbach plexus** (Little's area) is a common site for **anterior epistaxis**, especially in children and adolescents, because it is an aggregation of multiple converging arteries in the anterior septum.
- The failure of simple pressure and the patient's age make this region the most likely source for this intractable nosebleed due to its friability and common exposure to dryness or minor trauma.
*Ethmoidal artery*
- The ethmoidal arteries supply the **superior and posterior nasal cavities** and contribute to posterior epistaxis, which is typically more severe and less responsive to conservative measures.
- While an ethmoidal artery bleed could be intractable, it is generally less common than a Kiesselbach plexus bleed in a 14-year-old without trauma.
*Sphenopalatine artery*
- The **sphenopalatine artery** is a major contributor to **posterior epistaxis**, characterized by profuse bleeding that often drains into the pharynx, making it difficult to control with anterior packing.
- Though it can cause severe, intractable nosebleeds, it's less frequently the initial source in a young patient compared to the anterior septum, and the presentation doesn't strongly suggest posterior bleeding (e.g., blood flowing down the throat).
*Greater palatine artery*
- The **greater palatine artery** is a branch of the maxillary artery that supplies the hard palate and can contribute to posterior nasal bleeding, though it is less commonly implicated in epistaxis than the sphenopalatine or ethmoidal arteries.
- Bleeding from this vessel would typically present with posterior drainage and would be uncommon in a 14-year-old without trauma or other risk factors.
*Carotid artery*
- The carotid artery system is the primary blood supply to the nasal cavity, but a direct carotid artery bleed into the nose is **extremely rare** and usually due to severe trauma or erosion by a tumor or aneurysm.
- Such a bleed would be catastrophic and present with signs of critical hemorrhage, vastly different from this patient's relatively stable vital signs.
Nasal cavity and paranasal sinuses US Medical PG Question 8: A 54-year-old woman comes to the physician because of a 1-day history of fever, chills, and double vision. She also has a 2-week history of headache and foul-smelling nasal discharge. Her temperature is 39.4°C (103°F). Examination shows mild swelling around the left eye. Her left eye does not move past midline on far left gaze but moves normally when looking to the right. Without treatment, which of the following findings is most likely to occur in this patient?
- A. Hemifacial anhidrosis
- B. Jaw deviation
- C. Absent corneal reflex (Correct Answer)
- D. Relative afferent pupillary defect
- E. Hypoesthesia of the earlobe
Nasal cavity and paranasal sinuses Explanation: ***Absent corneal reflex***
- This patient's symptoms (fever, chills, headache, foul-smelling nasal discharge, periorbital swelling, and ophthalmoplegia) suggest **cavernous sinus thrombosis** secondary to a sinus infection.
- The cavernous sinus contains cranial nerves III, IV, VI, V1, and V2. Untreated, the infection and thrombosis can easily spread to affect **cranial nerve V1 (ophthalmic branch of trigeminal nerve)**, leading to an absent corneal reflex.
*Hemifacial anhidrosis*
- This symptom, along with ptosis and miosis, is indicative of **Horner's syndrome**, which results from damage to the ipsilateral **sympathetic pathway**.
- While cavernous sinus thrombosis can rarely involve sympathetic fibers, it's not the most direct or common neurological sequela compared to trigeminal nerve involvement.
*Jaw deviation*
- **Jaw deviation** typically occurs due to weakness or paralysis of the **motor branch of the trigeminal nerve (V3)**, which innervates the muscles of mastication.
- Cavernous sinus thrombosis primarily affects V1 and V2, and V3 involvement, while possible, is less common and usually presents later than V1 or V2 deficits.
*Relative afferent pupillary defect*
- A relative afferent pupillary defect (RAPD, or Marcus Gunn pupil) indicates a lesion in the **afferent visual pathway** (e.g., optic nerve or retina).
- While vision can be affected in cavernous sinus thrombosis due to optic nerve compression or venous congestion, RAPD is not the most direct or specific neurological complication expected from the provided symptoms.
*Hypoesthesia of the earlobe*
- Sensation to the earlobe is primarily supplied by the **great auricular nerve (C2-C3 cervical spinal nerves)** with minor contribution from the **auricular branch of the vagus nerve (CN X)**.
- Cavernous sinus thrombosis does not involve these nerves, and hypoesthesia of the earlobe is not a characteristic finding.
Nasal cavity and paranasal sinuses US Medical PG Question 9: Where does the only cranial nerve without a thalamic relay nucleus enter the skull?
- A. Superior orbital fissure
- B. Internal auditory meatus
- C. Foramen rotundum
- D. Jugular foramen
- E. Cribriform plate (Correct Answer)
Nasal cavity and paranasal sinuses Explanation: ***Cribriform plate***
- The **olfactory nerve (CN I)** is the only cranial nerve that does not have a thalamic relay nucleus before reaching the cerebral cortex.
- It passes through the **cribriform plate** of the ethmoid bone to reach the olfactory bulbs.
*Superior orbital fissure*
- This opening transmits the **oculomotor (CN III), trochlear (CN IV), ophthalmic division of trigeminal (CN V1)**, and **abducens (CN VI)** nerves.
- These nerves all have sensory or motor components that relay through the thalamus, directly or indirectly.
*Internal auditory meatus*
- This canal transmits the **facial (CN VII)** and **vestibulocochlear (CN VIII)** nerves.
- The vestibulocochlear nerve's auditory pathway involves a thalamic relay in the **medial geniculate nucleus**.
*Foramen rotundum*
- The **maxillary division of the trigeminal nerve (CN V2)** passes through the foramen rotundum.
- Sensory information carried by CN V2 relays through the **thalamus**.
*Jugular foramen*
- This opening transmits the **glossopharyngeal (CN IX), vagus (CN X)**, and **accessory (CN XI)** nerves.
- Sensory components of these nerves, particularly taste and visceral sensation, involve thalamic nuclei.
Nasal cavity and paranasal sinuses US Medical PG Question 10: A 31-year-old female undergoing treatment for leukemia is found to have a frontal lobe abscess accompanied by paranasal swelling. She additionally complains of headache, facial pain, and nasal discharge. Biopsy of the infected tissue would most likely reveal which of the following?
- A. Yeast with pseudohyphae
- B. Septate hyphae
- C. Irregular non-septate hyphae (Correct Answer)
- D. Spherules containing endospores
- E. Budding yeast with a narrow base
Nasal cavity and paranasal sinuses Explanation: ***Irregular non-septate hyphae***
- The clinical presentation of a **leukemic patient** with a **frontal lobe abscess** and **paranasal swelling**, along with headache, facial pain, and nasal discharge, strongly suggests **mucormycosis**.
- Mucormycosis is characterized by **broad, ribbon-like, irregular non-septate hyphae** with **right-angle branching** on tissue biopsy, making this the most likely finding.
*Yeast with pseudohyphae*
- This morphology is characteristic of **Candida species**, which can cause opportunistic infections but typically manifest as candidemia, esophagitis, or vulvovaginitis in immunocompromised patients, not usually a frontal lobe abscess with paranasal involvement.
- While Candida can cause severe systemic infections, the specific combination of a frontal lobe abscess and paranasal swelling points away from Candida as the primary cause in this context.
*Septate hyphae*
- **Septate hyphae** are typical of **Aspergillus species**, which can cause invasive aspergillosis, including sinopulmonary infections and CNS involvement in immunocompromised hosts.
- However, Aspergillus hyphae are typically **narrow (3-6 µm)** with **acute-angle (45-degree) branching**, differentiating them from the broad, irregular hyphae seen in mucormycosis.
*Spherules containing endospores*
- This morphology is characteristic of **Coccidioides immitis**, the causative agent of coccidioidomycosis.
- Coccidioidomycosis is geographically restricted to endemic areas (e.g., southwestern US) and typically presents with pulmonary symptoms, disseminated disease, or meningitis, which does not fit the described paranasal and frontal lobe presentation.
*Budding yeast with a narrow base*
- This morphology is characteristic of **Cryptococcus neoformans**, an encapsulated yeast that commonly causes **meningitis** and **pneumonia** in immunocompromised individuals.
- While Cryptococcus can cause CNS infections, the presence of paranasal swelling and the specific description of a frontal lobe abscess make mucormycosis a more fitting diagnosis.
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