Neuro Pathology - Lesion of the Medulla.

Locked-in syndrome is a bilateral pontine lesion affecting the ventral aspect of the pons as well as the nucleus of the 6th nerve. If it affects the cortico-spinal fibers, it leads to a loss of the bilateral paralysis of the upper extremities and the lower extremities causing quadriplegia, it would also lead to a lack of speech known as Aphonia. One final thing, if the abducens nerve is damaged as well as the oculomotor nerve causing an inability to move the eyes and loss of interaction with other nerves as a result of damage to medial longitudinal fasciculus leading to internuclear abdominoplasty where both abducens nerves are damaged.

In my last post I discussed Pontine Lesions as I began to write on Neuro pathology, today I will be discussing lesions of the medulla. Looking at the medulla, we can start with the dorsal medulla and the ventral medulla. At the dorsal part of the medulla is the hypoglossal nucleus, the dorsal nucleus of the Vagus, the nucleus of tractus solitarius, then the medial vestibular nucleus, and towards the lateral side is the inferior vestibular nucleus, then to the dorsal and ventral cochlea nuclei, then the inferior cerebellar peduncles, then the anterior spinal cerebellar tract. Also, in the medulla are the inferior olivary nucleus, corticospinal tracts, inferior salivatory nucleus, nuclus ambiguous, the medial lemniscus, spinal lemniscus, spinal nucleus of the trigeminal nerve, descending sympathetic tract, the tectospinal tract, the medial longitudinal fasciculus. ^{, ,} From the circle of Willis, the vertebral artery fuses together to make the basilar artery. When the artery gets to the midbrain they give the posterior cerebral artery. The vertebral artery also gives the anterior and the posterior spinal artery, also it gives the posterior inferior cerebella artery, the anterior inferior cerebella artery, and the superior cerebella artery. The Anterior Spinal Artery supplies the medial part of the medulla which could lead to the medial medullary syndrome if there is a lesion to the artery, if the posterior inferior cerebella artery is affected, causing the lateral medullary syndrome. ^{, ,}

If there is a lesion that affects the anterior spinal artery or a thrombosis in the artery, it would lead to the medial medullary syndrome. The hypoglossal nucleus and the nerve would get damaged, the medial lemniscus which is responsible for sensation, and the corticospinal tract would also get destroyed. When these structures are damaged, as a result of the spinal artery occlusion, the hypoglossal damage would cause genioglossus of the tongue which is responsible for the protrusion of the tongue would not function properly causing ipsilateral tongue deviation depending on the side of the hypoglossal nerve that is occluded. If the medial lemniscus receives fine and discriminative touch sensations from the skin, when there is a lesion, there is a contralateral loss of proprioception, vibrations, and touch sensation. When the corticospinal tract is damaged, there will be contralateral hemiplegia and weakness of the skeletal muscles. ^{, , ,}

Lateral medullary syndrome, there is a result of an occlusion of the posterior inferior cerebella artery. It involves the medial vestibular nucleus, inferior vestibular nucleus, nucleus ambiguous, spinal nucleus, descending sympathetic tract, inferior cerebella peduncle, and ventral cochlear nuclear. When the vestibular nuclei which are in the inner ear pick up static and dynamic equilibrium and send it to the 6th nerve nuclei which then send fibers to the medial longitudinal fasciculus which conjugates the eyes. When it is damaged, it will lead to loss of equilibrium presenting as vertigo leading to nausea and vomiting.^, If there is damage to the cochlear nuclei it would lead to unilateral neuro deafness. If there is damage to the descending sympathetic tract which supplies the muscle of the dilated pupil, the palpebra, and the sweat gland will lead to the inability to dilate the pupil, inability to elevate the upper eyelid, and inability to produce sweat known as Horner's syndrome. When the spinal nucleus and spinal tract is damaged, it would lead to an ipsilateral loss of facial sensations. When the Nucleus ambigus which carries special viceral Efferent Fibers which supplies the pharyngeal archies is damaged, it would affect the cranial nerve 9, 10, and 11, whose axons are from the nucleus ambigus and are known as pharyngeal plexus which supplies the pharynx, and the larynx. This would lead to dysphonia, dysatria, and weakness of the soft pallet. If the spinal Lemniscus which picks pain temperature, pressure sensation from the body is affected, it would lead to controlateral loss of touch, pain, temperature and pressure sensation.^{, , ,}