What is Corona Radiata?

Corona Radiata is a collection of nerve fibers present in the brain that carries messages between the brain cells of the cerebral cortex and the brain stem. Both brain stem and cerebral cortex play a role in motor function and sensation and it is the corona radiata that links both sensory and motor nerve pathways between these structures.

Structure of Corona Radiata

It is a fan-shaped array of white matter fibers that appears to merge inferiorly into the internal capsule. The corona fiberscross between the transversely oriented commissural fibers that meet at the corpus callosum. The fibers lie between the longitudinal fibers of the cingulum bundle and the superior front-occipital fasciculus medially and the superior longitudinal fasciculus laterally. Corticobulbar, corticospinal and corticopontine fibers descend within the internal capsule and corona radiata to enter the brainstem and spinal cord. The corona radiata merges dorsally with an oval-shaped amalgamation of projection, associational and commissural white matter tracts called the centrum semiovale that lies beneath the cerebral cortex.

The Function of Corona Radiata

• It is an important group of nerves that play a vital role in sending and receiving information between regions in the brain.

• The nerves present in the corona radiata are known as afferent and efferent as they carry information to and from the body respectively.

• The word afferent refers to sensory input and includes other input that is sent from the body to the brain.

• The word efferent refers to the information that is sent from brain to body to regulate motor function.

• Thus, corona radiata consists of afferent and efferent fibers that link the brain stem and the cerebral cortex.

Relationship between Internal Capsule and Corona Radiata

A deep subcortical structure that contains a bunch of afferent and efferent white matter projection fibers is known as the internal capsule. It is considered to be an important area due to the high concentration of motor and sensory projection fibers. The afferent fibers move from cell bodies of the thalamus to the cortex and efferent fibers move from cell bodies of the cortex to the middle peduncle of the midbrain. The internal capsule fibers supply to corona radiata. The internal capsule consists of five parts:

• Anterior limb: It lies medially and laterally between the head of the caudate nucleus and the lentiform nucleus respectively.
• Genu: It lies medial to the apex of the lentiform nucleus and contains corticonuclearfibers.
• Posterior limb: It lies between the thalamus medially and the lentiform nucleus laterally.
• Retrolentiform part: It is present at the back of lentiform nucleus and is composed ofgeniculocalcarine or optic radiation. The retolentiform part also includes corticopontine fibers.
• Sublentiform part: It underlies the lentiform nucleus which is composed of the temporopontinefibersand auditory radiations.

What Causes Damage in the Corona Radiata?

The injury caused due to a stroke in the corona radiata involves small branches of blood vessels. Various kinds of strokes that affect corona radiata include lacunar strokes, small vessel strokes, white matter strokes, and subcortical strokes.

Lacunar or small vessel strokes: It is known as lacunar or small blood vessel stroke as the corona radiata receives blood supply from small branches of the arteries in the brain. It is caused due to small vessel atherosclerosis and lipohyalinosis related to blood pressure or embolic occlusion. Due to the limited supply of these perforating end arteries, the obstruction results in small area infarction that ranges from 5-15mm in diameter. The infarctions area included are basal ganglia, thalamus, corona radiata, and internal capsule.

Multiple small strokes: Multiple strokes in corona radiata are also called cerebrovascular disease which is a condition that is featured by narrow, clot-prone blood vessels.

Silent strokes: Sometimes strokes in the corona radiata are small and may not show any symptoms. These strokes are referred to as silent strokes.

Alternatively, stroke in corona radiata can result in non-specific symptoms like not being able to care for oneself. These symptoms are considered stroke predictors even if the brain computerized tomography (CT) scan or brain magnetic resonance imaging (MRI) depicts no sign of a stroke.

Significance of Corona Radiata

Many research studies have pointed the role of corona radiata in predicting the stroke outcome. Using sophisticated imaging techniques, researchers have studied the metabolism of various regions of the brain in patients who have received a stroke. It was observed that the function of corona radiata within first 24 hours of a stroke was associated with the outcomes that were predicted after the stroke. Apart from stroke, there are various other problems like brain tumor, trauma in the head, brain infections, bleeding in the brain that disrupts the function of corona radiata.

How does Corona Radiata Appear in the CT of the Brain?

The internal capsule is a white matter tract that links with the corona radiata and white matter of the cerebral hemispheres superiorly, and with the brain stem inferiorly. The  corpus callosum interconnects the corona radiata on each side.

What are the Clinical Conditions where Corona Radiata is Affected?

• Cerebral venous thrombosis: In venous thrombosis, a cause of cerebral infarction is noticed. It has been reported that patients with bilateral corpus callosum and corona radiata infarction are found due to cerebral venous thrombosis with symptoms of headache and acute reversible aphasia.
• Ipsilateral hemiparesis: The condition is caused due to the infarction of corona radiata. The MRI studies demonstrated bilateral motor area activation during paretic left-hand movement. 
• Bipolar disorder: It is a disorder that occurs during periods of depression, elevated or irritable mood. The neuroimaging studies reveal that abnormalities related to the white matter are involved in bipolar disorder. Studies have shown that there is a lower fractional anisotropy in white matter tracts of the genu corpus callosum, bilateral anterior corona radiata in patients with bipolar disorder.
• Cheerio-oral syndrome: It has been reported that there is a small lesion in the contralateral corona radiata. CT studies showed a hypodense area in the right corona radiate.
• Ischemic stroke: Pontine and corona radiata are present in the same projections between the cortex and brain stem. It is the common site where the stroke involves the subcortical motor pathway. Stroke in these areas leads to extensive alterations of functions network centrality.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for      

• B.Sc. Biochemistry and Molecular biology        
• Bachelor of Molecular and cellular biology       
• M.Sc. Biological science
• M.Sc. in Biomolecular chemistry
• Masters in Biotechnology