detailed anatomy of the medulla
TRANSCRIPT
DETAILED ANATOMY OF THE MEDULLA
DR S.E.MBA
EXTERNAL FEATURES AND RELATIONS
• 3Cm long.• Located at the caudal portion of brainstem• Upper limit is cerebello-pontine angle• Transverse plane that above C1 (suboccipital n)
intersects upper border of atlas dorsally and centre of dens ventrally marks lower limit
• Ventral median fissure extends from foramen coecum to caudal end of pyramid decussation
• Lateral to median fissure is pyramid• Lat to pyramid is the ventrolateral sulcus (VLS)• Hypoglossal nerve rootlets emerge from VLS• Lat to VLS is olive which contains inf olivary nucleus• inferior cerebellar peduncle connects medulla with
cerebellum and forms side wall of caudal half of fourth ventricle
• At dorsal surface of closed part of medulla, gracile and cuneate fasciculi continue from the spinal cord
• Tuberculum cinereum, lateral to cuneate fasciculus marks the position of trigeminal spinal tract.
• Obex is apex of the V-shaped boundary of the inferior part of the fourth ventricle, which is folded caudally over the most rostral 1 to 2 mm of the central canal,
• The cochlear division of the vestibulocochlear nerve ends in the dorsal and ventral cochlear nuclei, which are situated on the base of the inferior cerebellar peduncle. The vestibular division penetrates the brain stem deep to the root of the inferior cerebellar peduncle.
• Roots of glossopharyngeal , vagus and cranial division of accessory nerves are attached to the medulla dorsal to olive.
VENTRAL ASPECT LATERAL ASPECT
DORSAL ASPECT
Chiari MalformationA 24-year-old woman presents with a long history of increasingheadache, blurred vision when attempting to read and an increasingly unsteady gait with intermittent falls. Neurological examination reveals downbeat nystagmus with the eyes in theprimary position, amplified by down-gaze; dysmetria of the lower extremities with heel-to-shin testing; and hyperreflexia in both lower extremities.
Downbeat nystagmus consists of a rapid downbeatmotion of the eyes followed by a slower upward movement. is characteristically associated with conditionsinvolving the medulla oblongata, particularly at thelevel of the craniocervical junction.
INTERNAL STRUCTURE
LATERAL MEDULLARY SYNDROME (WALLENBURG SYNDROME)1- Vestibular nuclei: vertigo, nausea, vomiting and nystagmus.2- Cerebellar peduncle: ataxia (gait/limb)3: Spinothalamic tract: controlateral loss of pain and temperature sensation4: Nucleus Ambiguus: palatal and laryngeal muscles paralysis..dysphagia and dysarthria5: Nucleus and spinal tract of V: ipsilateral analgesia and thermoanaesthesia of face6: Descending Sympathetic fibers: ipsilateral Horner’s syndrome: …………
WHICH ARTERY? PICA
MEDIAL MEDULLARY SYNDROME (AVELLIS’ SYNDROME)
• Pyramidal tract: contralateral hemiparesis• Medial lemniscus: contralateral loss of tactile discrimination• Hypoglossal Nerve: ipsilateral paralysis of tongue, deviation to same side
WHICH ARTERY? ANTERIOR SPINAL ARTERY (MEDULLARY BRANCHES)
CLINICAL SIGNIFICANCE OF MEDULLA• Raised Pressure in the Posterior Cranial Fossa and Its
Effect on the Medulla OblongataIn patients with tumors of the posterior cranial fossa, the intracranial pressure is raised, and the brain––that is, the cerebellum and the medulla oblongata––tends to be pushed toward the area of least resistance; there is a downward herniation of the medulla and cerebellar tonsils through the foramen magnum. This will produce the symptoms of headache, neck stiffness,and paralysis of the glossopharyngeal,vagus,accessory, and hypoglossal nerves owing to traction.
