A 14-year-old boy is brought to the emergency department because of acute left-sided chest pain and dyspnea following a motor vehicle accident. His pulse is 122/min and blood pressure is 85/45 mm Hg. Physical examination shows distended neck veins and tracheal displacement to the right side. The left chest is hyperresonant to percussion and there are decreased breath sounds. This patient would most benefit from needle insertion at which of the following anatomical sites?

2nd left intercostal space along the midclavicular line

5th left intercostal space along the midclavicular line

8th left intercostal space along the posterior axillary line

Subxiphoid space in the left sternocostal margin

5th left intercostal space along the midaxillary line

A 61-year-old woman comes to the physician for a follow-up examination 1 week after undergoing right-sided radical mastectomy and axillary lymph node dissection for breast cancer. She says that she has been unable to comb her hair with her right hand since the surgery. Physical examination shows shoulder asymmetry. She is unable to abduct her right arm above 90 degrees. When she pushes against a wall, there is protrusion of the medial aspect of the right scapula. Injury to which of the following nerves is the most likely cause of this patient's condition?

Upper trunk of the brachial plexus

A previously healthy 33-year-old woman comes to the physician because of pain and sometimes numbness in her right thigh for the past 2 months. She reports that her symptoms are worse when walking or standing and are better while sitting. Three months ago, she started going to a fitness class a couple times a week. She is 163 cm (5 ft 4 in) tall and weighs 88 kg (194 lb); BMI is 33.1 kg/m2. Her vital signs are within normal limits. Examination of the skin shows no abnormalities. Sensation to light touch is decreased over the lateral aspect of the right anterior thigh. Muscle strength is normal. Tapping the right inguinal ligament leads to increased numbness of the affected thigh. The straight leg test is negative. Which of the following is the most appropriate next step in management of this patient?

Advise patient to wear looser pants

Blood work for inflammatory markers

Surface anatomy for nerve blocks for USMLE Step 2 CK: High-Yield Anatomy Lessons

Upper Limb Blocks - Arm Yourself!

📌 Remember To Drink Cold Beer (Roots, Trunks, Divisions, Cords, Branches). Anesthetizes the arm, forearm, and hand.

Brachial Plexus, Phrenic Nerve, Subclavian Vein/Artery

Block	Nerve/Plexus Targeted	Key Surface Landmarks	Structures at Risk
Interscalene	Roots/Trunks (C5-C7)	Interscalene groove (between anterior/middle scalenes) at cricoid level (C6).	Phrenic nerve (100% transient paralysis), vertebral artery, stellate ganglion (Horner's).
Supraclavicular	Trunks/Divisions	"Supraclavicular fossa," superior to clavicle, lateral to SCM.	Pleura (highest pneumothorax risk), subclavian artery, phrenic nerve.
Infraclavicular	Cords	Inferior to clavicle, medial to coracoid process. Targets cords distal to clavicle.	Axillary artery/vein, pleura (↓ risk). Good for continuous catheters.
Axillary	Terminal Branches	Axilla, surrounding the palpable axillary artery. Requires multiple injections.	Axillary artery/vein (intravascular injection), musculocutaneous nerve often missed.

Lower Limb Blocks - A Leg Up

Ultrasound-guided femoral nerve block

Femoral Nerve Block
- Target: Femoral n. (L2-L4).
- Landmarks: Inguinal crease, lateral to femoral artery.
- 📌 NAVEL (Lateral to Medial): Nerve, Artery, Vein, Empty space, Lymphatics.
- Deficit: ↓ knee extension (quadriceps), ↓ sensation over anterior thigh, medial leg.
Sciatic Nerve Block
- Target: Sciatic n. (L4-S3).
- Landmarks: Midway between greater trochanter & ischial tuberosity.
- Deficit: Anesthetizes posterior thigh & most of leg/foot below the knee (spares saphenous distribution).
Popliteal Block
- Target: Sciatic n. in popliteal fossa.
- Landmarks: Popliteal crease.
- Deficit: Anesthesia for foot & ankle procedures; preserves hamstring function.

⭐ A femoral nerve block anesthetizes the anterior thigh and knee but spares the posterior leg and foot (sciatic distribution).

Head, Neck & Trunk - Core Coverage

Head & Neck
- Superficial Cervical Plexus Block: Injection at the midpoint of the posterior border of the sternocleidomastoid (SCM) muscle (“Erb's point”). Anesthetizes skin of anterolateral neck.
- Infraorbital Nerve Block: Target is the infraorbital foramen, located just inferior to the infraorbital rim, in line with the pupil.
- Mental Nerve Block: Injection at the mental foramen, inferior to the apex of the second mandibular premolar tooth.
Trunk
- Intercostal Nerve Block: Administered at the inferior margin of the rib to block the nerve running in the costal groove.
- Transversus Abdominis Plane (TAP) Block: Injection into the fascial plane between internal oblique and transversus abdominis muscles.

Surface anatomy of head, neck, and shoulder for nerve blocks

⭐ Exam Favourite: The Transversus Abdominis Plane (TAP) block targets nerves (T6-L1) between the internal oblique and transversus abdominis muscles for anterolateral abdominal wall analgesia.

High‑Yield Points - ⚡ Biggest Takeaways

Femoral nerve block: Landmark is the femoral artery pulse; inject just lateral to it, below the inguinal ligament.

Interscalene block: Between the anterior and middle scalene muscles at the cricoid cartilage level (C6).

Supraclavicular block: Targets the brachial plexus trunks/divisions; carries a significant pneumothorax risk.

Axillary block: The axillary artery is the central landmark, with nerves arranged predictably around it.

Popliteal sciatic block: Administered ~5-7 cm above the popliteal crease, between the hamstring tendons.

Ankle block: Requires five distinct injections to anesthetize the terminal nerves supplying the foot.

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