Neurological Evaluation Of The Lumbar Nerve Roots.

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Neurological Evaluation of Lumbar Nerve Roots

Overview

For any suspected lumbar nerve-root lesion, assess three things:

1. Sensory changes
   2. Motor changes
   3. Reflex changes

then works through L1, L2, L3, L4, L5, and S1 according to the level of disc herniation.

1. L1 Nerve Root

Disc level

T12–L1 disc herniation  -L1 nerve root

Sensory

describes the L1 sensory area as:

Region between the inguinal ligament and mid-thigh.

Motor

Hip flexion

Muscle mentioned:

• Iliopsoas

Roots contributing:

• L1, L2, L3

Reflex

No specific reflex for L1.

2. L2 Nerve Root

Disc level

L1–L2 disc herniation – L2 nerve root

Sensory

Mid-anterior thigh

Motor

associates L2 with:

• Hip flexion — L1, L2, L3
• Hip abduction — L2, L3, L4
• Knee extension — L2, L3, L4

Reflex

No specific reflex for L2.

3. L3 Nerve Root

Disc level

L2–L3 disc herniation – L3 nerve root

Sensory

Distal thigh, including the knee region

Motor

• Hip flexion — L1, L2, L3
• Hip abduction — L2, L3, L4
• Knee extension — L2, L3, L4

Reflex

No specific reflex for L3.

4. L4 Nerve Root

Disc level

L3–L4 disc herniation – L4 nerve root

Sensory

Medial side of the leg extending to the medial side of the foot

Motor

Important motor findings mentioned:

• Ankle dorsiflexion
  • Tibialis anterior
• Knee extension

Provocative test

A femoral stretch test may be positive.

Positive finding:

Pain in the ipsilateral anterior thigh

that this may suggest:

L3–L4 disc herniation affecting the L4 root

Reflex

Patellar reflex — mainly L4

5. L5 Nerve Root

Disc level

L4–L5 disc herniation – L5 nerve root

This is emphasized as a very important examination root.

Sensory

Dorsum of the foot and leg

For rapid recall:

Top of foot = L5

Motor

The two important motor functions emphasized are:

1. Great-toe extension

Great-toe extension = L5

This is one of the most useful examination findings.

2. Hip abduction

Muscles mentioned:

• Gluteus medius
• Gluteus minimus

links weakness here to:

Trendelenburg gait

Straight Leg Raise

SLR may be positive when the L5 nerve root is irritated.

uses SLR to help determine whether low-back pain has an underlying disc herniation with nerve-root irritation.

Reflex

No specific L5 reflex is emphasized in the transcript.

6. S1 Nerve Root

Disc level

L5–S1 disc herniation – S1 nerve root

Sensory

Lateral and plantar aspect of the foot

For quick recall:

Lateral foot = S1

Motor

Hip extension

Muscle:

• Gluteus maximus

notes that this is not commonly used clinically.

Ankle plantar flexion

This is emphasized as the more useful test.

Muscles:

• Gastrocnemius
• Soleus

Foot eversion

Muscles mentioned:

• Peroneus longus
• Peroneus brevis

Straight Leg Raise

SLR may also be positive with S1 root irritation.

Reflex

Ankle reflex = S1

High-Yield Lumbar Root Table

Root	Disc level affecting root	Sensory area	Main motor test	Reflex
L1	T12–L1	Inguinal region to upper/mid thigh	Hip flexion	None
L2	L1–L2	Mid-anterior thigh	Hip flexion / abduction / knee extension	None
L3	L2–L3	Distal thigh/knee region	Knee extension	None
L4	L3–L4	Medial leg ? medial foot	Ankle dorsiflexion, knee extension	Patellar
L5	L4–L5	Dorsum of foot	Great-toe extension, hip abduction	None emphasized
S1	L5–S1	Lateral/plantar foot	Ankle plantar flexion, eversion	Ankle

Most Important Roots: L4, L5, S1

specifically emphasizes these three roots.

Motor

• L4 – ankle dorsiflexion
• L5 – great-toe extension / hip abduction
• S1 – ankle plantar flexion

Sensory

• L4 – medial foot
• L5 – dorsum/top of foot
• S1 – lateral foot

Reflex

• L4 – patellar reflex
• S1 – ankle reflex

L5 has no specific reflex emphasized here.

Provocative Tests

Femoral Stretch Test

Useful mainly for upper lumbar/root irritation.

In this transcript:

Positive anterior-thigh pain may indicate L4 root involvement.

Straight Leg Raising Test

Used for suspected lower lumbar radiculopathy.

particularly associates it with:

• L5
• S1

A positive test suggests nerve-root irritation due to a possible herniated disc.

Practical Examination Sequence

For lumbar radiculopathy:

1. Identify sensory deficit
   2. Test corresponding motor function
   3. Check reflex
   4. Add nerve stretch test
   5. Correlate with probable disc level

Disc Level – Root Affected

A useful pattern from the transcript:

• T12–L1 disc – L1 root
• L1–L2 disc – L2 root
• L2–L3 disc – L3 root
• L3–L4 disc – L4 root
• L4–L5 disc – L5 root
• L5–S1 disc – S1 root

Key Take-Home Points

• Lumbar nerve-root examination is based on sensory + motor + reflex assessment.
• L4: medial leg/foot, ankle dorsiflexion, patellar reflex.
• L5: dorsum of foot, great-toe extension, hip abduction.
• S1: lateral/plantar foot, plantar flexion, ankle reflex.
• Trendelenburg gait may indicate weakness of L5-associated hip abductors in ‘s framework.
• Femoral stretch test may support upper lumbar/L4 irritation.
• SLR is useful for lower lumbar root irritation, especially L5/S1.
• places particular examination importance on L4, L5 and S1.

Exam Pearls

L4 – medial foot + dorsiflexion + knee jerk

L5 – dorsum of foot + EHL/great-toe extension + hip abduction

S1 – lateral foot + plantar flexion + ankle jerk

L4–L5 disc – L5 root

L5–S1 disc – S1 root