How to diagnose different types of radiculopathies of the cervical and lumbosacral region from history, physical examination, and motor, sensory testing. How to remember which nerve root supplies which dermatome, myotome, and reflexes, and muscles ? Also give images and illustrations to remember them easily .. Give me mnemonics wherever possible and make this topic easy for me to remember for my first FCPS Part 2 exam, MRCP and USMLE steps exam.

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cervical lumbosacral radiculopathy dermatome myotome reflex mnemonic USMLE MRCP

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lumbar radiculopathy L3 L4 L5 S1 dermatome myotome reflex table diagram illustration

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Radiculopathies: Cervical & Lumbosacral - Complete Exam Guide

The Big Picture First

Radiculopathy = nerve root compression giving a triad:

Pain radiating in a dermatomal pattern
Sensory loss/paresthesias in the dermatome
Motor weakness in the myotome + reflex loss

The key exam question is always: "Which level?" - answered by matching the pattern of weakness + sensory loss + reflex change.

PART 1: CERVICAL RADICULOPATHY

Anatomy Concept to Know First

The cervical nerve root exits above its numbered vertebra (C5 root exits between C4-C5). This means:

C4-C5 disc herniation → compresses C5 root
C5-C6 disc herniation → compresses C6 root
C6-C7 disc herniation → compresses C7 root
C7-T1 disc herniation → compresses C8 root

Mnemonic: "Cervical roots exit ABOVE = disc number = root below it"

C5, C6, C7 are the most commonly affected roots (levels of greatest cervical mobility and disc degeneration) - as confirmed in Bradley and Daroff's Neurology in Clinical Practice.

Cervical Radiculopathy at a Glance

Cervical radiculopathy - C5, C6, C7, C8 dermatomes, myotomes, and reflexes

The "5-6-7-8 Ladder" - Master Mnemonic for Cervical Roots

Root	Pain/Sensory area	Key Muscle	Test movement	Reflex	Mnemonic
C5	Shoulder/lateral arm	Deltoid, Biceps	Shoulder abduction	Biceps	"C5 = Shoulder shrug/abDuct"
C6	Lateral forearm, thumb + index	Biceps, Brachioradialis, Wrist extensors	Elbow flexion + wrist extension	Brachioradialis	"C6 = siX-pack thumb (thumb is digit 1=index)"
C7	Middle finger, posterior arm	Triceps, Wrist flexors, Pronators	Elbow extension	Triceps	"C7 = sEVEn = EXTEND (triceps)"
C8	Ring + little finger, medial forearm	Finger flexors, Intrinsics	Grip strength / finger flexion	None	"C8 = grEIGHt (grip)"
T1	Medial upper arm	Intrinsics (interossei)	Finger abduction/adduction	None	"T1 = Tiny interossei"

Master Mnemonic: "BiBoTri-No" = C5 Biceps / C6 Brachioradialis / C7 Triceps / C8 No reflex

Or remember: B-B-T going down = Biceps (C5-C6), Brachioradialis (C6), Triceps (C7).

C5 Radiculopathy (C4-C5 disc)

History: Pain from neck → shoulder → lateral arm. Weakness lifting arm overhead. Dermatome: Lateral shoulder, lateral upper arm ("epaulette" area) Myotome weak: Deltoid (shoulder abduction), Biceps, Supraspinatus Reflex lost: Biceps jerk (C5-C6) Tip: Patient cannot comb their hair or lift arm above shoulder. "Shoulder problem, but no neck trauma."

Test: Resisted shoulder abduction - patient holds arm at 90° while you push down.

C6 Radiculopathy (C5-C6 disc) - Most common cervical level

History: Pain down lateral forearm into thumb + index finger. "My thumb goes numb." Dermatome: Lateral forearm, thumb, index finger, lateral half of palm Myotome weak: Biceps (elbow flexion), Brachioradialis, Wrist extensors (ECRL, ECRB) Reflex lost: Biceps jerk AND Brachioradialis jerk Special sign: "Inverted" or "paradoxical" brachioradialis reflex (tap BR → finger flexors contract but no BR contraction = myelopathy at same level)

Test: Resisted elbow flexion + resisted wrist extension

C7 Radiculopathy (C6-C7 disc) - Most common overall

History: Pain to middle finger (± ring finger). Weakness pushing things away ("can't do push-ups"). Subscapular/interscapular pain is classic. Dermatome: Middle finger, dorsal forearm, posterior arm Myotome weak: Triceps, Wrist flexors (FCR, FCU), Pronator teres, Finger extensors Reflex lost: Triceps jerk (ONLY reflex exclusively for C7) Tip: Triceps jerk = C7 exclusively. Test by tapping triceps tendon with elbow at 90°.

Test: Resisted elbow extension

C8 Radiculopathy (C7-T1 disc)

History: Pain/numbness to ring + little finger, medial forearm. Clumsy hand. Dermatome: Medial forearm, ring + little finger Myotome weak: Finger flexors (FDP, FDS), Intrinsic hand muscles, Abductor pollicis brevis Reflex: No dedicated reflex (a common exam trap!) Tip: C8 looks like ulnar nerve but SNAPS are normal in radiculopathy (preganglionic lesion)

T1 Radiculopathy

History: Medial upper arm pain/numbness, intrinsic hand weakness (often Pancoast tumor should be excluded) Dermatome: Medial upper arm, inner elbow Myotome: Intrinsic hand muscles (interossei, lumbricals) Exam: Finger abduction/adduction weakness, look for Horner syndrome (ptosis, miosis, anhidrosis) - suggests Pancoast tumor

Special Provocation Tests for Cervical Radiculopathy

Test	Technique	What positive means	Sens/Spec
Spurling Test	Extend neck + side-bend toward painful side + axial compression downward	Reproduces radicular arm pain	Low sensitivity, HIGH specificity
Cervical Distraction Test	Patient supine, lift head with hands under chin/occiput	Relief of radicular pain	Moderate sens, high spec
Upper Limb Tension Test (ULTT)	Scapular depression + shoulder abduction/flexion + elbow/wrist/finger extension, neck laterally bent away	Reproduces arm/hand pain	HIGH sensitivity (~90%), low specificity
Shoulder Abduction Relief Sign	Patient raises hand/arm above head	Relieves pain	Specific for C4-5 or C5-6
Valsalva/Cough	Increases intrathecal pressure	Worsens radicular pain	-----

From Textbook of Family Medicine: Spurling test = low sens, high spec. Upper limb tension test = sensitivity >90%, low specificity. Straight-leg raise (lumbar) = sensitivity 91%, specificity 26%.

Mnemonic for Spurling: "SPECific for radiculopathy" = Spurling = SPECificity

PART 2: LUMBOSACRAL RADICULOPATHY

Key Anatomy Concept

In the lumbar region, roots exit below their numbered vertebra (unlike cervical). However, the disc at L4-L5 typically compresses the traversing L5 root (not L4), because L4 exits at L4-L5 foramen:

L3-L4 disc → compresses L4 root (exiting at L3-L4 foramina) or traversing L4
L4-L5 disc herniation → usually compresses traversing L5 root
L5-S1 disc herniation → usually compresses traversing S1 root

Most common: S1 (from L5-S1 disc) and L5 (from L4-L5 disc)

Lumbosacral Radiculopathy Table

L4, L5, S1 disc herniations with clinical findings and cauda equina

Body Dermatome Map

Lumbar Root Summary Table

Root	Disc Level	Pain Pattern	Key Weakness	Reflex Lost	Sensory Area	Mnemonic
L2	L1-L2	Anterior thigh	Hip flexion	None	Anterior/medial upper thigh	"L2 = Loin to groin"
L3	L2-L3	Anterior thigh → medial knee	Knee extension, hip adduction	Patellar (partial)	Anterior thigh + medial knee	"L3 = Leg thREE, thigh/knee"
L4	L3-L4	Anterior thigh → medial shin	Knee extension (quads), foot inversion	Patellar/Knee jerk	Medial lower leg	"L4 = 4ward = kneecap"
L5	L4-L5	Buttock → lateral leg → dorsum foot → big toe	Foot/great toe dorsiflexion (EHL), hip abduction	Ankle jerk (sometimes, medial)	Lateral leg, dorsum foot, big toe	"L5 = L5ift foot up, big toe"
S1	L5-S1	Buttock → posterior thigh → lateral foot	Plantar flexion (calf), eversion	Ankle jerk / Achilles	Posterior thigh, calf, lateral foot/heel	"S1 = Soles of feet, Sole=S1, Ankle jerk"
S2-4	-	Perineum, inner thighs	Bladder/bowel, sphincters	Bulbocavernosus/anal	Saddle area	"S2,3,4 keeps the poo off the floor"

Lumbosacral Root Mnemonics

"2-3-4 in front, 5-1 behind"

L2, L3, L4 radiculopathies → pain anteriorly (anterior thigh, medial leg) - tested by Femoral nerve stretch test
L5, S1 → pain posteriorly (buttock, posterior leg) - tested by Straight Leg Raise (SLR)

Key Reflex Mnemonics

Reflex	Root	Mnemonic
Biceps	C5-C6	"B5-6 = Biceps 5 and 6"
Brachioradialis	C6	"BR = Brachioradialis = Rad-6"
Triceps	C7	"Tri7 = Triceps C7"
Patellar (knee jerk)	L3-L4	"Patellar = L3-L4, knee goes fore"
Achilles (ankle jerk)	S1	"Aching S1 ankle" or "S1 = Sole/Achilles"

The "L4-L5-S1 Clinical Triad" (Exam Favourite)

Feature	L4	L5	S1
Weakness	Knee extension, foot inversion	Dorsiflexion of foot/big toe	Plantar flexion (stand on tiptoe)
Sensory	Medial shin	Dorsum foot, big toe	Lateral foot, heel
Reflex	Knee jerk ↓	Ankle jerk (sometimes) or absent	Ankle jerk ↓
Quick test	Walk on heels (tests L4/L5)	Cannot lift big toe	Cannot stand on tiptoes
Disc	L3-L4	L4-L5	L5-S1

Memory hook:

L4 = "4wards walking" = knee extension, heel walking
L5 = "L5ft the foot up" = dorsiflexion, extensor hallucis longus (EHL)
S1 = "S1 = Sole" = plantar flexion, ankle jerk

Clinical Provocation Tests for Lumbosacral Radiculopathy

Test	Technique	Roots tested	Sens/Spec
Straight Leg Raise (SLR / Lasègue)	Supine, passively raise straight leg. Positive: radicular pain at 30-70° (NOT just back pain)	L5, S1	Sensitivity 91%, specificity 26%
Crossed SLR	Raising the contralateral leg reproduces ipsilateral radicular pain	L5, S1	Low sensitivity, high specificity (~90%)
Femoral Nerve Stretch Test	Prone, flex knee to 90°, extend hip. Positive: anterior thigh pain	L2, L3, L4	For upper lumbar roots
Slump Test	Seated, slump forward + extend knee + dorsiflex ankle. Positive: sciatic pain	L5, S1	High sensitivity
Bowstring Sign	After positive SLR, flex knee slightly - if pain returns with popliteal fossa pressure, positive	L5, S1	High specificity

Key from Rheumatology textbook: Femoral stretch test = L2/L3/L4; SLR/Bowstring = L5/S1

Mnemonic: "SLR for LOW (L5-S1 = low lumbar), Femoral for HIGH (L2-3-4 = upper lumbar)"

PART 3: RED FLAGS (Cauda Equina - Must Not Miss!)

Cauda equina syndrome = massive central disc herniation (usually L4/5 or L5/S1) compressing multiple roots:

Bilateral leg pain/weakness
Saddle anesthesia (S2-4 dermatome - perineum, inner thighs)
Bladder retention or incontinence (most reliable sign)
Anal sphincter laxity (loss of anal tone)
Decreased/absent bilateral ankle jerks

"Saddle + Bladder = Emergency Surgery" - From Bradley and Daroff's and Textbook of Family Medicine: sphincter disturbance from lumbar disease requires urgent surgical consideration.

Historical red flags for any back pain:

Fever, weight loss (infection/malignancy)
History of cancer
Bowel/bladder dysfunction (CES)
Saddle anesthesia
Bilateral leg weakness
Recent major trauma
IV drug use / immunosuppression

PART 4: DIAGNOSTIC INVESTIGATIONS

Test	Radiculopathy Finding	Notes
MRI spine	Disc herniation or osteophyte compressing root	Investigation of choice
CT myelography	Same as MRI; better for calcified lesions, post-op patients	If MRI contraindicated
NCS	Normal SNAPs (lesion is preganglionic, proximal to DRG)	Differentiates from peripheral neuropathy
EMG (needle)	Fibrillations/PSWs in myotome distribution + paraspinals	Confirms radiculopathy; paraspinals are key
F-waves	May be delayed in affected root	Less sensitive
H-reflex	Absent/asymmetric = S1 radiculopathy (sensitivity 50%, specificity 91%)	Very specific for S1

Key NCS point for exams: In radiculopathy, the dorsal root ganglion (DRG) is outside the spinal canal, so sensory axons peripheral to the DRG are intact → SNAPs normal despite sensory symptoms. CMAPs may be reduced if significant motor axon loss. This distinguishes radiculopathy from peripheral neuropathy/plexopathy.

"Normal SNAP = preganglionic = radiculopathy" - Bradley and Daroff's Neurology

PART 5: MASTER MEMORY TABLE

Upper Limb Reflexes - "BiBoTri No" Mnemonic

C5 = Biceps (and Brachioradialis shares)
C6 = Brachioradialis (and Biceps shares)
C7 = Triceps (exclusive)
C8 = Nothing (no reflex)

Lower Limb Reflexes

L3-L4 = Patellar (knee jerk)  → "kneecap = L34"
S1    = Achilles (ankle jerk) → "sole/ankle = S1"

PART 6: DERMATOMAL KEY LANDMARKS (USMLE/MRCP Favourites)

Landmark	Root
Nipple line	T4
Xiphoid process	T7
Umbilicus	T10
Groin / inguinal ligament	L1
Anterior thigh	L2-L3
Medial shin/knee	L4
Dorsum of foot / big toe	L5
Lateral foot / heel / sole	S1
Perineum / saddle area	S2-S4

Thoracic landmarks mnemonic: "T4 = Tits (nipples), T10 = TEN = Tummy button (umbilicus)"

PART 7: HISTORY TAKING - THE RADICULOPATHY TEMPLATE

A structured history for FCPS/MRCP/USMLE OSCEs:

Character of pain: burning, shooting, lancinating (neuropathic quality)
Radiation: Does it radiate beyond the knee (lumbar) or elbow (cervical)?
Aggravating factors: Cough/sneeze/Valsalva worsens → increased intrathecal pressure → radiculopathy
Relieving factors: Arm raised above head relieves cervical pain (shoulder abduction relief sign)
Duration and onset: Acute (disc) vs. gradual (spondylosis/stenosis)
Neurological symptoms: Numbness, tingling in which finger/toe?
Weakness: Specific activities - can't open jars (C8/T1), can't comb hair (C5), can't walk on tiptoes (S1), dragging foot (L5)
Red flags: Bilateral, bowel/bladder, saddle numbness

Quick Summary Card for Exams

Cervical

C5: Shoulder abduction weak, Biceps reflex ↓, lateral arm numb
C6: Elbow flex + wrist extend weak, Brachioradialis reflex ↓, thumb/index numb - most common
C7: Elbow extend weak, Triceps reflex ↓, middle finger numb
C8: Finger flex weak, NO reflex, ring/little finger numb
Spurling = high spec, ULTT = high sens

Lumbosacral

L4: Quad/knee extend weak, Knee jerk ↓, medial shin numb, heel walk
L5: Foot/big toe dorsiflex weak (EHL), ankle jerk sometimes ↓, dorsum foot/big toe numb
S1: Plantar flex weak (calf), Ankle jerk ↓, lateral foot numb, tiptoe test
SLR tests L5/S1 (high sens), Femoral stretch tests L2/L3/L4 (high spec)
Cauda equina = saddle anesthesia + bladder = EMERGENCY

Sources: Bradley and Daroff's Neurology in Clinical Practice (cervical radiculopathy chapters); Textbook of Family Medicine 9e (spine physical examination tables); Lecturio medical illustrations; neurological examination evidence from PMC scoping review on cervical radiculopathy.

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