Peripheral Nerve Blocks: Upper Extremity — MCQs
Which nerve supplies the area marked as ‘Area B’ in the image?
In doing phrenic nerve block, it is best to infiltrate
Which block is described as regional anesthesia of the arm:-
The most common complication of interscalene block:-
To give a field block, the LA should be deposited near
Most commonly used nerve for monitoring during anesthesia
Which approach of brachial plexus block targets cords of the brachial plexus:-
What is the name of the nerve block technique shown in the image?
All of the following are complications of epidural anaesthesia, EXCEPT:
Interscalene approach to brachial plexus block does not provide optimal surgical anaesthesia in the area of distribution of which of the following nerve?
Peripheral Nerve Blocks: Upper Extremity Indian Medical PG Practice Questions and MCQs
Question 1: Which nerve supplies the area marked as ‘Area B’ in the image?
- A. Ulnar nerve
- B. Median nerve
- C. Radial nerve (Correct Answer)
- D. Posterior interosseous nerve
Explanation: ***Radial nerve*** - Area B represents the sensory distribution of the **radial nerve**, specifically its superficial branch. - The radial nerve provides sensory innervation to the **dorsal (back) aspect of the hand** over the radial (lateral) side, including the thumb, index, middle, and radial half of the ring finger up to the proximal interphalangeal joints. - The superficial branch of the radial nerve also innervates the **anatomical snuffbox** and the radial side of the dorsum of the hand. - **Note:** The radial nerve does NOT supply the palmar surface of the hand; its sensory distribution is limited to the dorsal aspect. *Ulnar nerve* - The ulnar nerve provides sensory innervation to the **medial 1.5 fingers** (little finger and ulnar half of ring finger) on both palmar and dorsal aspects. - It also supplies the **hypothenar eminence** and medial portion of the palm and dorsal hand. - This distribution corresponds to **Area C** in the image, not Area B. *Median nerve* - The median nerve provides sensory innervation to the **lateral 3.5 fingers** (thumb, index, middle, and radial half of ring finger) on the **palmar surface**. - It also supplies the **palmar aspect** of these digits and the **nail beds (dorsal tips)** of the same fingers. - This distribution corresponds to **Area A** in the image, not Area B. *Posterior interosseous nerve* - The **posterior interosseous nerve (PIN)** is a **motor branch** of the radial nerve with no cutaneous sensory distribution. - It supplies the extensor muscles of the posterior forearm compartment. - It does not provide sensory innervation to the skin of the hand.
Question 2: In doing phrenic nerve block, it is best to infiltrate
- A. Scalenus anterior
- B. Scalenus posterior
- C. Anterior border of sternomastoid
- D. Posterior border of sternomastoid (Correct Answer)
Explanation: Posterior border of sternomastoid - The phrenic nerve (C3-C5) descends on the anterior surface of the scalenus anterior muscle through the neck. - To block the phrenic nerve as it emerges from the brachial plexus roots, local anesthetic is ideally infiltrated at the posterior border of the sternomastoid muscle at the level of the cricoid cartilage (C6 vertebral level). Scalenus anterior - While the phrenic nerve rests on the anterior surface of the scalenus anterior, infiltrating this muscle directly might not be as effective for a complete block, as the nerve is relatively superficial at the posterior border of the sternomastoid. - Infiltration within the scalenus anterior could potentially lead to a less targeted block or hit other structures within the muscle. Scalenus posterior - The scalenus posterior muscle is located deeper and more laterally in the neck compared to the scalenus anterior. - The phrenic nerve does not have a direct anatomical relationship with the scalenus posterior that would make this an optimal site for a block. Anterior border of sternomastoid - The anterior border of the sternomastoid muscle provides an anatomical landmark for other neck structures, but the phrenic nerve is not readily accessible for blockade at this specific location. - Infiltrating here would be too anterior and medial to where the phrenic nerve emerges from the brachial plexus components.
Question 3: Which block is described as regional anesthesia of the arm:-
- A. Interscalene block
- B. Infraclavicular block
- C. Axillary block
- D. Supraclavicular brachial plexus block (Correct Answer)
Explanation: ***Supraclavicular brachial plexus block*** - The **supraclavicular block** targets the **trunks of the brachial plexus** as they exit the scalene muscles, providing comprehensive anesthesia to the entire upper limb, including the shoulder, arm, forearm, and hand. - This block is particularly effective for procedures involving the arm due to its proximal location within the brachial plexus, covering multiple nerve distributions. *Interscalene block* - An **interscalene block** primarily targets the **roots or trunks of the brachial plexus** and is typically used for shoulder and upper arm surgery, but may spare the ulnar nerve. - While it anesthetizes the arm, it is primarily chosen for more proximal procedures and may not provide complete distal arm anesthesia compared to the supraclavicular approach. *Infraclavicular block* - An **infraclavicular block** targets the **cords of the brachial plexus** and is suitable for procedures involving the elbow, forearm, and hand, providing good coverage for these areas. - While it does anesthetize the distal arm, it is more distal than the supraclavicular block and may not provide full coverage for the entire upper arm and shoulder. *Axillary block* - An **axillary block** targets the **terminal branches of the brachial plexus** in the axilla, mainly anesthetizing the forearm and hand. - This block is often used for procedures distal to the elbow and provides less comprehensive coverage for the entire upper arm and shoulder compared to more proximal blocks.
Question 4: The most common complication of interscalene block:-
- A. Pneumothorax
- B. Phrenic block (Correct Answer)
- C. Hypotension
- D. Horner syndrome
Explanation: ***Phrenic block*** - The **phrenic nerve** runs anterior to the anterior scalene muscle within the **interscalene groove**, making it highly susceptible to local anesthetic spread during an interscalene block. - This complication is very common, occurring in nearly all patients, and can lead to **hemidiaphragmatic paresis**, causing a decrease in pulmonary function. *Pneumothorax* - While a serious complication of interscalene block, **pneumothorax** is relatively rare because the pleura is not typically in the needle's path with proper technique. - It usually occurs due to an accidental puncture of the **pleural membrane**, leading to air accumulation in the pleural space. *Hypotension* - **Hypotension** is not a primary or most common complication of an interscalene block, which primarily targets nerves supplying the shoulder and arm. - Significant hypotension would more likely be associated with systemic absorption of local anesthetic or a central neuraxial block. *Horner syndrome* - **Horner syndrome** can occur when the **stellate ganglion** (part of the sympathetic chain) is blocked due to the spread of local anesthetic from the interscalene groove to the paravertebral space. - Although it is a recognized complication, it is less common than phrenic nerve block and typically resolves spontaneously.
Question 5: To give a field block, the LA should be deposited near
- A. Main trunk
- B. Small nerve endings
- C. Periodontal ligament
- D. Large branch of peripheral nerve (Correct Answer)
Explanation: ***Large branch of peripheral nerve*** - A **field block** involves depositing local anesthetic near a larger sensory nerve branch to anesthetize a wider area of tissue distal to the injection site. - This method effectively blocks nerve impulses before they innervate smaller nerve endings, providing a broader area of numbing compared to infiltration. *Main trunk* - Depositing local anesthetic near the **main nerve trunk** (e.g., inferior alveolar nerve block) represents a **nerve block**, not a field block. - Nerve blocks aim to anesthetize an entire region supplied by that major nerve, which is usually more extensive than a field block. *Small nerve endings* - Injecting local anesthetic near **small nerve endings** is characteristic of **local infiltration** anesthesia. - This method provides localized anesthesia to a small, circumscribed area, which is less extensive than a field block. *Periodontal ligament* - Injecting into the **periodontal ligament** is a specific technique called an **intraligamentary injection**, primarily used for single-tooth anesthesia. - This method targets the dental nerve fibers entering the apex of the tooth and is not a field block.
Question 6: Most commonly used nerve for monitoring during anesthesia
- A. Facial nerve
- B. Ulnar nerve (Correct Answer)
- C. Radial nerve
- D. Median nerve
Explanation: ***Ulnar nerve*** - The **ulnar nerve** is most commonly used for **neuromuscular monitoring** during anesthesia due to its accessibility at the wrist and predictable response to stimulation. - Stimulation typically elicits an adductor pollicis contraction, which is easily observed and quantified with various monitoring devices. *Facial nerve* - The **facial nerve** is primarily monitored during **neurosurgical procedures** where facial nerve integrity is at risk, such as parotidectomy or acoustic neuroma resection. - While it can be monitored, it is not the standard choice for general neuromuscular blockade assessment due to its complex innervation patterns and the need for specific electrode placement. *Radial nerve* - The **radial nerve** is less frequently used for standard neuromuscular monitoring compared to the ulnar nerve. - Its stimulation can lead to more variable and less quantifiable thumb or finger extension, making it less ideal for precise assessment of blockade depth. *Median nerve* - The **median nerve** can be used for neuromuscular monitoring, often stimulating the thenar muscles to produce thumb flexion. - However, it is generally considered a secondary site compared to the ulnar nerve due to greater anatomical variability in electrode placement and response.
Question 7: Which approach of brachial plexus block targets cords of the brachial plexus:-
- A. Infraclavicular (Correct Answer)
- B. Supraclavicular
- C. Axillary
- D. All of the options
Explanation: ***Infraclavicular*** - The **infraclavicular approach** targets the brachial plexus at the level of the **cords**, which lie deep to the pectoralis muscles and medial to the coracoid process. - This block is particularly useful for surgeries involving the **distal upper limb**, as it blocks all divisions of the cords. *Supraclavicular* - The **supraclavicular approach** targets the brachial plexus at the level of the **trunks**, specifically where they emerge between the anterior and middle scalene muscles. - While it provides good anesthesia for the entire upper limb, it is proximal to the cord level. *Axillary* - The **axillary approach** targets the terminal nerves (e.g., median, ulnar, radial, musculocutaneous) after the brachial plexus has divided into individual nerves in the **axilla**. - This block is distal to the cords and is often used for surgeries of the forearm and hand. *All of the options* - This option is incorrect because only the **infraclavicular approach** specifically targets the cords of the brachial plexus. - The other approaches target either the trunks (supraclavicular) or the terminal nerves (axillary).
Question 8: What is the name of the nerve block technique shown in the image?
- A. Intra-arterial anesthesia (Correct Answer)
- B. Bier's block
- C. Regional anesthesia
- D. Axillary block
Explanation: ***Intra-arterial anesthesia*** - The image shows a **cannula inserted directly into an artery**, indicated by the blood reflux and the context of anesthesia, suggesting direct drug delivery into the arterial system. - This method is used for specific types of regional pain management or diagnostic procedures where direct arterial access is required for **localized drug distribution**. *Bier's block* - A Bier's block, or **intravenous regional anesthesia**, involves injecting local anesthetic into a **vein** in an extremity after it has been exsanguinated and isolated by a tourniquet. - The image clearly shows a **bright red blood flash**, characteristic of arterial cannulation, not venous. *Regional anesthesia* - This is a broad term referring to the **anesthesia of a specific region** of the body and encompasses various techniques. - While intra-arterial anesthesia is a type of regional anesthesia, "regional anesthesia" itself is too general to specifically describe the technique shown. *Axillary block* - An **axillary block** is a type of peripheral nerve block targeting the brachial plexus in the axilla to anesthetize the arm. - The image does not depict the axillary region or the characteristic needle placement for an axillary block; instead, it shows direct vascular access.
Question 9: All of the following are complications of epidural anaesthesia, EXCEPT:
- A. Urinary retention
- B. Total spinal analgesia
- C. Hypopnoea
- D. Hypertension (Correct Answer)
Explanation: ***Hypertension*** - Epidural anesthesia commonly causes **vasodilation** and a subsequent drop in **blood pressure** (hypotension), not hypertension, due to sympathetic blockade. - While hypertension can occur due to pain or anxiety during the procedure, it is not a direct physiological complication of the epidural anesthetic itself. *Urinary retention* - Epidural anesthesia can affect the nerves controlling the **bladder**, leading to temporary **urinary retention**. - This is a common complication, often requiring catheterization until the epidural wears off. *Total spinal analgesia* - This occurs if the epidural needle inadvertently punctures the **dura** and a large dose of local anesthetic is injected into the **subarachnoid space**. - It results in widespread **sensory and motor blockade**, potentially leading to respiratory arrest and hemodynamic collapse. *Hypopnoea* - High epidural blocks or accidental **intrathecal administration** can cause paralysis of **intercostal muscles** and the diaphragm. - This can lead to **respiratory depression** (hypopnoea) or even apnea, necessitating ventilatory support.
Question 10: Interscalene approach to brachial plexus block does not provide optimal surgical anaesthesia in the area of distribution of which of the following nerve?
- A. Median
- B. Musculocutaneous
- C. Radial
- D. Ulnar (Correct Answer)
Explanation: ***Ulnar*** - The **ulnar nerve** (C8-T1) emerges from the lower trunk of the brachial plexus. During an **interscalene block**, the local anesthetic is typically deposited at the level of the roots and trunks (C5-C7), which is superior to the origin of the lower trunk that gives rise to the ulnar nerve. - Due to the **cephalad spread** of the local anesthetic from an interscalene block, the **C8 and T1** nerve roots (and thus the ulnar nerve) are often not adequately blocked, leading to suboptimal anesthesia in its distribution. *Median* - The **median nerve** (C5-T1) originates from the lateral and medial cords, which are typically well-covered by the spread of local anesthetic in an interscalene block due to its formation from the middle and upper trunks. - Optimal anesthesia in the distribution of the median nerve is generally achieved with an interscalene block, as its nerve roots are within the targeted antegrade spread. *Musculocutaneous* - The **musculocutaneous nerve** (C5-C7) arises from the lateral cord, which is formed by the upper and middle trunks. These structures are reliably blocked during an interscalene approach. - Sensory and motor functions of the musculocutaneous nerve, such as **biceps contraction** and lateral forearm sensation, are usually well anesthetized. *Radial* - The **radial nerve** (C5-T1) is a branch of the posterior cord, which receives fibers from all three trunks. Its upper and middle trunk components are generally well-blocked by an interscalene approach. - While complete anesthesia of the entire brachial plexus can be variable, the radial nerve is more consistently affected by an interscalene block than the ulnar nerve due to its more extensive proximal root contributions which are within the typical spread.
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