Ocular Ultrasound — MCQs
Ultrasound is the best initial investigation of choice for:
Signs of increased intracranial tension are all except:
The earliest manifestation of increased intracranial pressure following head injury is:
Avascular structure of the eye is -
Which mode of ultrasonography is used to measure the axial length of the eyeball?
Among the following non-auditory signs, which appears earliest in acoustic neuroma?
Which inhalational agent increases intracranial pressure most significantly?
The position of the patient as shown below is favored for which of the following conditions?
A patient is placed in the **lateral decubitus position** (lying on their side with knees drawn toward the chest and the spine flexed/arched outward) before the procedure. This position is maintained during which of the following types of anaesthesia?
During ultrasound-guided internal jugular vein cannulation, you observe the vein collapsing with minimal probe pressure while the artery remains patent. The vein appears enlarged and the artery-to-vein ratio is 1:3. A spontaneously breathing patient shows respiratory variation. Evaluate the most appropriate interpretation and management strategy.
Ocular Ultrasound Indian Medical PG Practice Questions and MCQs
Question 1: Ultrasound is the best initial investigation of choice for:
- A. Somatostatinoma
- B. Intraductal Pancreatic calculi
- C. Urethral stricture
- D. Blunt abdominal trauma (Correct Answer)
Explanation: ***Blunt abdominal trauma*** - **Focused Assessment with Sonography for Trauma (FAST) exam** is the initial imaging modality of choice for rapidly detecting **intra-abdominal free fluid** (hemoperitoneum) in hemodynamically unstable patients with blunt abdominal trauma due to its speed, portability, and non-invasiveness. - It helps guide the need for further imaging or surgical intervention, making it critical in the acute setting. *Urethral stricture* - The gold standard for diagnosing urethral strictures is **urethrography** (retrograde urethrogram), which directly visualizes the stricture and its extent. - While ultrasound can sometimes be used to assess the urethra, it is less effective than urethrography for defining the length and severity of a stricture. *Intraductal Pancreatic calculi* - Often best visualized with **Endoscopic Retrograde Cholangiopancreatography (ERCP)** or **Magnetic Resonance Cholangiopancreatography (MRCP)**, which provide detailed imaging of the pancreatic and bile ducts. - While transabdominal ultrasound can sometimes detect dilated ducts or large calculi, **Endoscopic Ultrasound (EUS)** is more sensitive and specific for intraductal pathologies, making routine transabdominal ultrasound not the primary choice. *Somatostatinoma* - Diagnosed primarily through biochemical tests (elevated **somatostatin levels**) and imaging like **CT, MRI, or somatostatin receptor scintigraphy (SRS)**, which are superior for localizing these rare neuroendocrine tumors. - Although ultrasound can sometimes detect pancreatic masses, it is not the **investigation of choice** for definitive diagnosis or staging of somatostatinomas.
Question 2: Signs of increased intracranial tension are all except:
- A. Headache
- B. Seizures
- C. Papilledema
- D. Tachycardia (Correct Answer)
Explanation: ***Tachycardia*** - **Tachycardia** is generally *not* a sign of increased intracranial pressure (ICP); rather, **bradycardia** (Cushing's reflex) is a classic finding. - While other systemic responses may occur, a direct, consistent increase in heart rate due to elevated ICP is uncommon. *Papilledema* - **Papilledema** is a swelling of the **optic disc** due to increased ICP, a critical diagnostic sign [1]. - The increased pressure impedes venous return from the retina, causing the optic nerve head to bulge. *Headache* - **Headache** is a common and often early symptom of increased ICP due to the stretching of pain-sensitive meningeal and vascular structures [1]. - It is typically described as a dull, throbbing pain, often worse in the morning or with straining. *Seizures* - **Seizures** can result from increased ICP as the pressure on brain tissue can lead to electrical instability and abnormal neuronal discharge [2]. - This symptom indicates significant cortical irritation or dysfunction caused by the elevated pressure.
Question 3: The earliest manifestation of increased intracranial pressure following head injury is:
- A. Hemiparesis
- B. Ipsilateral pupillary dilatation
- C. Altered mental status (Correct Answer)
- D. Contralateral pupillary dilatation
Explanation: ***Altered mental status*** - **Altered mental status** (e.g., confusion, irritability, drowsiness) is often the earliest sign of increased intracranial pressure (ICP) due to its profound effect on global brain function. - This change reflects the **brain's reduced perfusion** and metabolic compromise as pressure within the rigid skull rises. *Hemiparesis* - **Hemiparesis** indicates focal neurological deficits, usually resulting from direct injury or significant pressure on specific motor pathways, which typically manifest later than global mental status changes. - It suggests a more advanced stage of neurological compromise or a localized mass effect. *Ipsilateral pupillary dilatation* - **Ipsilateral pupillary dilatation** is a classic sign of uncal herniation, where the temporal lobe compresses the **oculomotor nerve** (CN III) on the same side. - While critical, it is generally a *late and ominous sign* of significantly elevated ICP, indicating severe brainstem compression. *Contralateral pupillary dilatation* - **Contralateral pupillary dilatation** is highly unusual in the context of typical uncal herniation, which almost always causes *ipsilateral* signs due to direct compression. - Its presence would suggest atypical herniation patterns or other causes of pupillary asymmetry.
Question 4: Avascular structure of the eye is -
- A. Retina
- B. Cornea (Correct Answer)
- C. Ciliary body
- D. Conjunctiva
Explanation: ***Cornea*** - The **cornea** is transparent and relies on **aqueous humor** for nutrients and oxygen directly from the air and tears, making it avascular. - Its avascularity is crucial for maintaining **transparency**, which is essential for light transmission to the retina. *Retina* - The retina is a highly **metabolically active** tissue that requires a rich blood supply. - It receives blood primarily from the **choroid** and the central retinal artery. *Ciliary body* - The ciliary body is part of the **uvea** and is highly vascular, responsible for producing **aqueous humor**. - It contains the **ciliary muscle**, which controls the shape of the lens for accommodation. *Conjunctiva* - The conjunctiva is a **vascular mucous membrane** lining the inner surface of the eyelids and covering the anterior sclera. - Its blood vessels are visible and can become **engorged** during inflammation or irritation (e.g., conjunctivitis).
Question 5: Which mode of ultrasonography is used to measure the axial length of the eyeball?
- A. A-mode Ultrasonography (Correct Answer)
- B. B-mode Ultrasonography
- C. M-mode Ultrasonography
- D. None of the options
Explanation: ***A-mode Ultrasonography*** - **A-mode** (amplitude modulation) ultrasonography is a **one-dimensional** display that measures the distance between structures based on the time it takes for sound waves to reflect. - It is specifically used for **biometry**, such as measuring the axial length of the eyeball for **intraocular lens (IOL) power calculation** prior to cataract surgery. *B-mode Ultrasonography* - **B-mode** (brightness modulation) ultrasonography provides a **two-dimensional** image, displaying the cross-sectional anatomy of organs. - While useful for visualizing ocular structures, it is not primarily used for precise **axial length measurements**. *M-mode Ultrasonography* - **M-mode** (motion mode) ultrasonography displays the **movement** of structures over time in a one-dimensional format. - This mode is typically used in **cardiac imaging** to assess heart valve motion and chamber dimensions, not for static length measurements of the eye. *None of the options* - This option is incorrect because **A-mode ultrasonography** is indeed the gold standard for measuring the axial length of the eyeball. - The other modes (B-mode and M-mode) serve different diagnostic purposes in ultrasonography.
Question 6: Among the following non-auditory signs, which appears earliest in acoustic neuroma?
- A. Congestion of conjunctiva
- B. Diplopia
- C. Diminished corneal sensitivity (Correct Answer)
- D. Ptosis
Explanation: ***Diminished corneal sensitivity*** - The **corneal reflex** is mediated by the **trigeminal nerve (CN V)**, which has a close anatomical relationship with the vestibulo-cochlear nerve (CN VIII) within the cerebellopontine angle. - Early compression of CN V by an enlarging **acoustic neuroma** can lead to diminished corneal sensitivity before more widespread neurological deficits appear. *Congestion of conjunctiva* - This symptom is non-specific and not directly associated with the early stages of an **acoustic neuroma**. - Conjunctival congestion can be caused by various factors, including irritation, allergies, or infections, and does not indicate cranial nerve involvement. *Diplopia* - **Diplopia (double vision)** typically occurs due to involvement of the extraocular motor nerves (CN III, IV, or VI) or brainstem compression. - This is generally a later sign and requires significant tumor growth to affect these structures, making it less likely to be an earliest non-auditory symptom. *Ptosis* - **Ptosis (drooping eyelid)** is caused by dysfunction of the oculomotor nerve (CN III) or the sympathetic nervous system (Horner's syndrome). - These nerves are usually affected later in the course of an **acoustic neuroma** once the tumor has grown significantly and compressed adjacent structures distant from its initial growth site.
Question 7: Which inhalational agent increases intracranial pressure most significantly?
- A. Halothane (Correct Answer)
- B. Sevoflurane
- C. Isoflurane
- D. Desflurane
Explanation: ***Halothane*** - **Halothane** causes a greater increase in **cerebral blood flow** and thus **intracranial pressure (ICP)** compared to newer volatile anesthetics due to its more potent cerebral vasodilation. - Its use has largely declined due to concerns about its effects on ICP and potential for **hepatotoxicity**. *Sevoflurane* - While sevoflurane can cause **cerebral vasodilation** and increase ICP, its effect is generally less pronounced than halothane, especially when normocapnia is maintained. - It is often favored in neuroanesthesia due to its rapid onset and offset, allowing for quicker adjustments in anesthetic depth. *Isoflurane* - Isoflurane causes less cerebral vasodilation and a smaller increase in ICP compared to halothane, particularly at lower concentrations. - It maintains **cerebral vascular autoregulation** better than halothane, helping to preserve a more stable ICP. *Desflurane* - Desflurane also causes cerebral vasodilation and can increase ICP, but its effect is typically less significant than halothane. - Rapid increases in desflurane concentration can lead to sympathetic stimulation and transient increases in blood pressure, which can indirectly affect ICP.
Question 8: The position of the patient as shown below is favored for which of the following conditions?
- A. CHF
- B. Air embolism
- C. Neurosurgery
- D. Raised ICP (Correct Answer)
Explanation: ***Raised ICT*** - The image depicts the patient in a **reverse Trendelenburg position** (head elevated). This position is often used to reduce **intracranial pressure (ICP)** by promoting venous drainage from the brain. - Elevating the head above the trunk aids in gravity-assisted drainage of cerebral venous blood and cerebrospinal fluid, thereby lowering ICP and preventing complications like brain herniation. *CHF* - Patients with **congestive heart failure (CHF)** often prefer a **Fowler's position** (sitting upright) to ease breathing and reduce pulmonary congestion, not the reverse Trendelenburg as shown. - Lying flat or with feet elevated in CHF can worsen dyspnea and increase cardiac workload due to increased venous return. *Air embolism* - For suspected **air embolism**, the patient is typically placed in the **Trendelenburg position** (head down, feet up) with a left lateral tilt to trap air in the right ventricle and prevent it from entering the pulmonary circulation. - This position helps prevent air from crossing into the left side of the heart thereby reducing the risk of systemic arterial air embolization. *Neurosurgery* - While neurosurgery often involves specific patient positioning, the depicted position isn't uniquely favored for neurosurgery in general. Positioning depends on the surgical site. - The **reverse Trendelenburg** is specifically used when reducing ICP is a primary goal during or after neurosurgical procedures, but not all neurosurgeries.
Question 9: A patient is placed in the **lateral decubitus position** (lying on their side with knees drawn toward the chest and the spine flexed/arched outward) before the procedure. This position is maintained during which of the following types of anaesthesia?
- A. Spinal anaesthesia (Correct Answer)
- B. Bier's block
- C. Caudal anaesthesia
- D. Stellate block
Explanation: ***Spinal anaesthesia*** - The **lateral decubitus position** with flexed spine and knees drawn to chest maximally opens the **intervertebral spaces**, facilitating needle insertion into the **subarachnoid space**. - This **fetal position** increases the distance between spinous processes, making identification of anatomical landmarks easier for **lumbar puncture**. *Bier's block* - Requires the patient in **supine position** with the affected limb elevated to achieve **exsanguination** before tourniquet application. - The procedure involves **intravenous injection** into a peripheral vein of the isolated limb, not spinal positioning. *Caudal anaesthesia* - Typically performed in **prone position** or **jack-knife position** to provide optimal access to the **sacral hiatus**. - The lateral decubitus position does NOT facilitate access to the **caudal epidural space** through the sacrococcygeal membrane. *Stellate block* - Requires **supine position** with slight **neck extension** to access the **anterior paratracheal space** at C6-C7 level. - The lateral decubitus position would make identification of **cervical landmarks** and **carotid artery** extremely difficult and unsafe.
Question 10: During ultrasound-guided internal jugular vein cannulation, you observe the vein collapsing with minimal probe pressure while the artery remains patent. The vein appears enlarged and the artery-to-vein ratio is 1:3. A spontaneously breathing patient shows respiratory variation. Evaluate the most appropriate interpretation and management strategy.
- A. This indicates hypovolemia; fluid resuscitation should be considered before central line insertion (Correct Answer)
- B. This is normal anatomy; proceed with cannulation using standard technique
- C. This suggests venous thrombosis; consider alternative site
- D. This indicates increased central venous pressure; use ultrasound compression technique
Explanation: ***This indicates hypovolemia; fluid resuscitation should be considered before central line insertion*** - Significant **respiratory variation** and ease of **venous collapse** with minimal probe pressure are classic ultrasound indicators of a **low intravascular volume state**. - Managing the **hypovolemia** first improves the safety of the procedure by increasing the target vessel size, thereby reducing the risk of **accidental arterial puncture**. *This is normal anatomy; proceed with cannulation using standard technique* - While the **internal jugular vein** is normally larger than the artery, excessive **compressibility** and collapse indicate an abnormal physiological state that complicates cannulation. - Proceeding without addressing the **underfilled vein** increases the technical difficulty and the likelihood of a **transfixion injury** where the needle passes through both walls. *This suggests venous thrombosis; consider alternative site* - **Venous thrombosis** would manifest as a **non-compressible** vein, often containing visible **distal echoes** or intraluminal clots. - In this scenario, the vein is noted to be **highly compressible**, which is the physiological opposite of what is seen in **deep vein thrombosis (DVT)**. *This indicates increased central venous pressure; use ultrasound compression technique* - High **central venous pressure (CVP)** would result in a **distended, non-collapsible** vein that does not vary significantly with the respiratory cycle. - An **artery-to-vein ratio** where the vein is excessively small or collapses easily specifically contradicts the diagnosis of **fluid overload** or **right heart failure**.
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