All are true regarding brachial plexus injury, except:

Preganglionic lesions have a better prognosis than postganglionic lesions

In Klumpke's palsy, Horner's syndrome may be present on the ipsilateral side

Erb's palsy causes paralysis of the abductors and external rotators of the shoulder

Histamine test is useful to differentiate between the preganglionic and postganglionic lesions

A 55-year-old male, known smoker, complains of calf pain while walking. He experiences calf pain while walking but can continue walking with effort. Which grade of claudication does this patient fall under?

Grade II (Moderate claudication)

Grade III (Severe claudication)

Which nerve is responsible for supplying the posterior semicircular canal?

Inferior vestibular nerve supplying posterior semicircular canal

Superior vestibular nerve supplying posterior semicircular canal

Superior vestibular nerve supplying anterior semicircular canal

Inferior vestibular nerve supplying anterior semicircular canal

Which of the following statements about the brachial plexus is true?

Formed by spinal nerves C5-C8 and T1

The radial nerve arises from the medial cord of the brachial plexus.

Injury to the brachial plexus may occur during shoulder dystocia, often affecting the lower trunk.

The lower trunk is a common site of injury in brachial plexus trauma.

Cervical Plexus for FMGE: High-Yield Anatomy Lessons

Plexus Formation - Neck's Nerve Nexus

Definition: A nerve network in the neck providing cutaneous and motor innervation to structures in the neck and supero-thoracic region.
Vertebral Levels: Formed by the ventral rami of spinal nerves C1-C4.
- Often receives a contribution from C5 (especially for the phrenic nerve).
Location: Lies deep to the Sternocleidomastoid (SCM) muscle and prevertebral fascia, anterior to the Scalenus Medius and Levator Scapulae muscles.
Formation: Arises from a series of communicating loops (ansae) between the ventral rami of C1, C2, C3, and C4.

⭐ A key contribution to the phrenic nerve often comes from the C5 ventral ramus, joining the primary roots from C3 and C4. Remember: "C3, C4, C5 keeps the diaphragm alive."

Plexus Branches - Nerve Pathways Charted

The cervical plexus gives rise to superficial (sensory) and deep (motor) branches.

Sensory branches emerge at Erb's point (posterior border of SCM). 📌 Mnemonic for sensory branches: L-G-T-S (Lesser occipital, Great auricular, Transverse cervical, Supraclavicular).

Cervical Plexus Diagram

Branch Details:

Nerve Name	Root Value(s)	Type	Innervation/Distribution
*Superficial (Sensory)*
Lesser Occipital	C2	Sensory	Skin of scalp posterosuperior to auricle
Great Auricular	C2, C3	Sensory	Skin over parotid, mastoid, auricle, angle of mandible
Transverse Cervical	C2, C3	Sensory	Skin of anterior & lateral neck
Supraclavicular	C3, C4	Sensory	Skin over shoulder, clavicle, upper pectoral region
*Deep (Motor)*
Ansa Cervicalis	C1, C2, C3	Motor	Infrahyoid muscles (sternohyoid, sternothyroid, omohyoid)
- Superior Root	C1	Motor	From C1 (travels with CN XII); to sup. belly omohyoid, upp. sternohyoid/thyroid
- Inferior Root	C2, C3	Motor	From C2,C3; to inf. belly omohyoid, low. sternohyoid/thyroid
Phrenic Nerve	C3, C4, C5	Motor & Sensory	Diaphragm (sole motor); sensory to diaphragm, pericardium, pleura
Segmental Branches	C1-C4	Motor	Prevertebral muscles (longus colli/capitis), scalenes, levator scapulae & some strap muscles (e.g. thyrohyoid via C1)

Clinical Significance - When Nerves Cry Out

Cervical Plexus Block: Regional anesthesia for neck/shoulder procedures.
- Superficial Block:
  - Sensory nerves; landmark: Erb's point (mid-posterior SCM border).
- Deep Block:
  - Nerve roots (motor/sensory); landmarks: Chassaignac's tubercle (C6), mastoid.
  - ⚠️ Risks: Phrenic nerve block, vertebral artery/subarachnoid injection.
Phrenic Nerve Palsy (C3,C4,C5 keep diaphragm alive 📌):
- Causes: Trauma (surgical, iatrogenic e.g., interscalene block), tumor compression.
- Signs: Dyspnea (esp. supine/exertion), paradoxical abdominal movement (abdomen in on inspiration), unilateral elevated diaphragm (CXR).
Referred Pain:
- Diaphragmatic irritation (e.g., peritonitis, cholecystitis) → shoulder tip pain.
- Mechanism: Shared C3-C5 segments for Phrenic n. (diaphragm) & Supraclavicular n. (shoulder).

⭐ Erb's point (punctum nervosum): Emergence of 4 superficial cervical plexus branches (Lesser occipital, Great auricular, Transverse cervical, Supraclavicular) at posterior SCM border.

High‑Yield Points - ⚡ Biggest Takeaways

Formed by ventral rami of C1-C4 spinal nerves.

Phrenic nerve (C3, C4, C5) is vital, innervating the diaphragm.

Ansa cervicalis (C1-C3 loop) supplies most infrahyoid muscles.

Four main cutaneous branches provide sensation to the neck, ear, and clavicular region.

These sensory nerves emerge at Erb's point, a key landmark for cervical plexus block.

Deep motor branches also supply prevertebral muscles, scalenes, and levator scapulae.

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Cervical Plexus