Focused anatomy lesson
Spinothalamic Tracts
Spinothalamic tracts are ascending pathways in the spinal cord. They carry sensory information from the body toward the thalamus, a relay region deep within the brain. From there, the information continues to the cerebral cortex, where sensations can be consciously recognised.
The system is usually described as two related pathways: the anterior spinothalamic tract and the lateral spinothalamic tract. Together, they contribute to the perception of light touch, pressure, pain, and temperature.
In one sentence
The spinothalamic system is an ascending sensory route that helps the brain identify potentially important changes in touch, pressure, pain, and temperature.
Anatomy
The two tracts are found in each half of the spinal cord. The anterior tract lies toward the front, while the lateral tract lies toward the side. Their fibres form part of the anterolateral system, a group of pathways that carries several kinds of sensory information upward.
Location
The pathways extend through the spinal cord and continue into the brainstem. Their organisation is paired, so each side of the cord contains pathways associated with information entering from both sides of the body after the fibres cross near their entry level.
Pathway in three steps
Cell bodies are located in the dorsal root ganglia. Peripheral branches receive signals from sensory receptors, while central branches enter the spinal cord.
These neurons lie in the posterior grey matter. Their axons cross to the opposite side and ascend through the anterolateral spinal cord.
These neurons are found in the ventral posterolateral nucleus of the thalamus and send information onward through the internal capsule.
Signals reach the primary somatosensory cortex in the postcentral gyrus, where the brain can interpret their location and quality.
Final destination
As the tracts ascend, they pass through the brainstem as part of the spinal lemniscus before reaching the thalamus. Third-order neurons then project to the primary somatosensory cortex in the parietal lobe.
Physiology
The two named pathways are associated with overlapping but distinct types of sensation.
Anterior spinothalamic tract
This tract is commonly linked with light touch and pressure. These sensations help the brain detect contact with an object or a force applied to the skin.
Lateral spinothalamic tract
This tract is commonly linked with pain and temperature. These signals can alert the brain to tissue threat or a potentially harmful hot or cold surface.
What happens when pathways are affected?
Damage to the spinothalamic pathways can alter the perception of pain, temperature, touch, or pressure. The pattern depends on the location, extent, and timing of the injury or disease, so symptoms should always be interpreted by a qualified clinician.
Examples used in neuroanatomy
- Tabes dorsalis: a late complication of untreated syphilis that can affect sensory roots and related pathways.
- Hemisection of the spinal cord: damage to one side can produce a characteristic pattern of sensory change below the affected level.
- Complete spinal cord injury: interruption of the cord can affect sensory and motor communication below the lesion.
Summary
Spinothalamic tracts are ascending spinal pathways involved in carrying pain, temperature, light touch, and pressure information. First-order neurons begin in dorsal root ganglia, second-order fibres cross within the spinal cord, and third-order neurons relay information from the thalamus to the primary somatosensory cortex.
This page is an educational overview, not a diagnostic tool. A healthcare professional should assess new or changing sensory symptoms.
References for further study
- Snell’s Clinical Neuroanatomy, Wolters Kluwer.
- Costanzo Physiology, Wolters Kluwer.
- Gray’s Clinical Neuroanatomy, Elsevier.