Examination Of S1 Nerve Root - Everything You Need To Know - Dr. Nabil Ebraheim скачать в хорошем качестве

Examination Of S1 Nerve Root - Everything You Need To Know - Dr. Nabil Ebraheim

Dr. Ebraheim’s educational animated video describes examination of the S1 nerve root. Examination of the S1 nerve root. There are three elements for examination of the S1 nerve root: sensory examination, motor examination and reflex examination. The sensory examination is easy. You examine the lateral side of the foot, as you can see here. We know the top of the foot is L5 and the medial side of the foot is L4. So, the sensation of the foot goes from S1 to L5 to L4 on the foot. The reflex is easy also. One reflex, Achilles tendon reflex. The motor is a little bit complicated because there's a lot of muscles that are innervated by the S1 nerve root. So, what are the muscles innervated by the S1? Will be the peroneus longus and brevis. Will be the flexor hallucis longus. Will be the gastrocnemius and the lateral hamstrings. The lateral hamstring is the biceps femoris. And the gluteus maximus. So, from proximal to distal, it will be the gluteus maximus, the lateral hamstring, the gastrocnemius, the flexor hallucis longus, and the peroneus longus and brevis. So, a patient with a herniated disc at L5 S1, affecting S1 nerve root could have imaging changes in these muscles. You may find sharp waves or fibrillations. A posterolateral herniated disc at L5 S1 clearly causes S1 nerve root irritation. But a foraminal herniated disc at L5 S1 will cause L5 radiculopathy. And if you have an L5 S1 isthmic spondylolisthesis, then that will cause L5 radiculopathy. In contrast to S1, the L5 nerve root will involve the extensor hallucis longus and the extensor digitorum longus. Will also involve the medial hamstring and the gluteus medius. The L5 nerve root involvement will come from posterolateral disc herniation at L4, L5 level. There is no reflex for L5, but there will be decreased sensation on the top of the foot. Quiz Questions: 1. Which sensory area corresponds specifically to the S1 nerve root? A) Top of the foot B) Medial side of the foot C) Lateral side of the foot D) Heel of the foot Answer: Lateral side of the foot Explanation: The sensory innervation of the lateral aspect of the foot is supplied by the S1 nerve root. 2. Which reflex specifically tests the integrity of the S1 nerve root? A) Patellar reflex B) Achilles tendon reflex C) Babinski reflex D) Tibialis posterior reflex Answer: Achilles tendon reflex Explanation: The Achilles tendon reflex predominantly tests the S1 nerve root. 3. Which muscle listed is innervated by the S1 nerve root? A) Extensor hallucis longus B) Extensor digitorum longus C) Medial hamstring D) Flexor hallucis longus Answer: Flexor hallucis longus Explanation: The flexor hallucis longus muscle receives innervation from the S1 nerve root. 4. What nerve root involvement occurs with an L5-S1 posterolateral disc herniation? A) L4 nerve root B) L5 nerve root C) S1 nerve root D) Both L4 and L5 nerve roots Answer: S1 nerve root Explanation: A posterolateral disc herniation at L5-S1 typically compresses and irritates the S1 nerve root. 5. Which clinical condition usually leads to L5 radiculopathy rather than S1 radiculopathy? A) Posterolateral herniated disc at L5-S1 B) Foraminal herniated disc at L5-S1 C) Posterolateral disc herniation at L4-L5 D) Foraminal herniated disc at L4-L5 Answer: Foraminal herniated disc at L5-S1 Explanation: A foraminal herniation at L5-S1 typically affects the L5 nerve root, not the S1 nerve root. 6. What finding on electromyography (EMG) suggests S1 nerve root irritation? A) Increased voluntary contraction B) Normal motor unit potentials C) Sharp waves or fibrillations D) Large amplitude potentials Answer: Sharp waves or fibrillations Explanation: Sharp waves and fibrillations on EMG indicate acute denervation consistent with nerve root irritation. 7. Which muscle is innervated by L5 rather than S1 nerve root? A) Gluteus maximus B) Lateral hamstring C) Peroneus brevis D) Extensor hallucis longus Answer: Extensor hallucis longus Explanation: The extensor hallucis longus muscle is innervated primarily by the L5 nerve root. 8. Which of the following conditions causes L5 radiculopathy rather than S1? A) Posterolateral disc herniation at L5-S1 B) L5-S1 isthmic spondylolisthesis C) L4-L5 lateral recess stenosis D) Posterolateral disc herniation at L3-L4 Answer: L5-S1 isthmic spondylolisthesis Explanation: Isthmic spondylolisthesis at L5-S1 typically causes L5 nerve root compression rather than S1. 9. Which of these muscles is NOT innervated by the S1 nerve root? A) Gastrocnemius B) Gluteus maximus C) Peroneus longus D) Gluteus medius Answer: Gluteus medius Explanation: The gluteus medius muscle is innervated primarily by the L5 nerve root. 10. A patient with S1 radiculopathy will likely show weakness in what action? A) Ankle dorsiflexion B) Knee extension C) Ankle plantar flexion D) Hip abduction Answer: Ankle plantar flexion Explanation: S1 nerve root primarily innervates muscles responsible for ankle plantar flexion, such as the gastrocnemius.