Cervical radicular syndromes: causes and anatomy
The main cause of cervical radiculopathies is intervertebral foraminal stenosis secondary to osteochondrosis. Due to the decreased height of the intervertebral disc, the body of the upper vertebra descends, increasing pressure on the uncinate processes (processus uncinatus). This leads to their bony remodeling and narrowing of the lumen of the foramina through which nerve roots (radices nervorum), blood vessels, and adipose tissue pass.
The process may involve one or multiple segments, most frequently the $C_V–C_{VI}$ and $C_{VI}–C_{VII}$ levels. Clinically, root irritation presents with pain and paresthesias, while severe compression manifests as hypalgesia, paresis, and loss of reflexes.
Topography of cervical root lesions
Each cervical root supplies a specific dermatome, reflex, and muscle group:
- C5 root: pain in the shoulder girdle, weakness of the deltoid (m. deltoideus) and biceps brachii (m. biceps brachii) muscles.
- C6 root: pain in the C6 dermatome, weakness of the biceps brachii and brachioradialis (m. brachioradialis) muscles, and decreased biceps reflex.
- C7 root: pain in the middle finger region, weakness of the triceps brachii (m. triceps brachii) and pronator teres (m. pronator teres) muscles, and decreased triceps reflex.
- C8 root: pain in the medial regions, weakness and atrophy of the hypothenar muscles (eminentia hypothenaris), and decreased Trömner's reflex.
Lumbar radicular syndromes and biomechanics
In the lumbar spine, disc degeneration leads to protrusions and herniations. Due to the anatomical course of the roots, a posterolateral protrusion typically does not damage the root of its own level, but instead compresses the root of the underlying segment. The two lower discs ($L_V-S_I$ and $L_{IV}-L_V$) are the most vulnerable.
- L3 and L4 roots: pain in the corresponding dermatome, weakness of the quadriceps femoris (m. quadriceps femoris) muscle, and decreased knee jerk reflex.
- L5 root: weakness of the extensor hallucis longus (m. extensor hallucis longus) muscle, pain and sensory disturbances along the anterolateral surface of the shin.
- S1 root: weakness of the triceps surae (m. triceps surae) and peroneal muscles, and loss of the Achilles reflex.
Dangerous complications: cauda equina syndrome
A large median lumbar disc herniation can rupture the posterior longitudinal ligament (lig. longitudinale posterius) and progress into a sequestered hernia. A free disc fragment in the spinal canal causes cauda equina syndrome (Cauda equina), which requires emergency surgical intervention.
Acute root compression with cessation of impulse conduction indicates critical ischemia and the threat of axonal death, for which conservative therapy is powerless.
Briefly: answers to topical questions
What clinical symptoms constitute cauda equina syndrome?
Cauda equina syndrome manifests as the sequential development of pain and neurological deficit. The clinical picture includes the following symptoms:
- Pain — the primary symptom, often acute pain in both legs.
- Sensory disturbances — numbness in the legs and anogenital region (saddle anesthesia).
- Peripheral lower limb paresis — accompanied by the loss of Achilles reflexes.
- Pelvic organ dysfunction — urinary and fecal incontinence, loss of sensation of their passage, impotence.
- Absence of the anal reflex.
Which muscles are part of the L5 root myotome?
The L5 root myotome includes the following key muscles:
- Extensor hallucis longus (m. extensor hallucis longus).
- Extensor digitorum brevis (m. extensor digitorum brevis).
Where are sensory disturbances localized in C8 radiculopathy?
Sensory disturbances in C8 spinal nerve root lesions are localized within the innervation zone of the corresponding dermatome. They include pain, paresthesias, and hypalgesia in the following areas:
- Medial surface of the forearm — predominantly the lower medial part (medial border of the distal third).
- Medial surface of the hand — inner aspect of the hand.
- Fingers — IV (ring) and V (little) fingers.
Which conduction pathways are located in the lateral funiculi of the spinal cord?
Both motor and sensory conduction pathways are located in the lateral funiculi of the spinal cord.
- Motor pathways (in the central part) — lateral corticospinal and rubrospinal tracts.
- Sensory pathways (in the periphery) — anterior and lateral spinothalamic tracts (pathways for superficial sensibility), as well as the anterior and posterior (lateral) spinocerebellar tracts (pathways for unconscious proprioception).
Which alternating syndromes are characteristic of midbrain peduncle lesions?
Midbrain lesions in the area of the cerebral peduncles are characterized by the development of the following alternating syndromes:
- Weber's syndrome — manifests as oculomotor nerve palsy on the side of the lesion and contralateral central hemiplegia.
- Benedikt's syndrome — characterized by oculomotor nerve palsy on the side of the lesion combined with contralateral cerebellar ataxia (hemiataxia).
Cervical roots correspond to their vertebra from top to bottom, while lumbar posterolateral hernias always "strike one level lower" — pinching the root of the underlying segment.
Class and exam questions
Why does a dorsolateral lumbar disc herniation affect the traversing (lower) nerve root?
The root, descending toward its intervertebral foramen, passes directly posterior to the bulging disc of the overlying segment.
Which muscles serve as indicator muscles for the C6 nerve root?
Biceps brachii (m. biceps brachii) and brachioradialis (m. brachioradialis) muscles.
What causes acute lumboischialgia other than disc herniations?
A frequent cause is impingement of the articular capsule in the facet joint during sudden movements.
What else to study on this topic
- Anatomical structure of the intervertebral foramen and the role of uncinate processes
- Mechanisms of capsular impingement formation in facet joints
- Topography of nerve plexuses (cervical, brachial, and lumbosacral)
- Difference between symptoms of root irritation and loss of function
- Indications for emergency neurosurgical intervention in compression
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