Neuroanatomy - Firecracker Flashcards
Where are the different sinuses located?
- The superior sagittal sinus is located in the falx cerebri
- The confluence sinuses brings together the superior saggital sinus and straight sinus - branches into the transverse sinuses
- The transverse sinuses lie on the margins of the tentorium cerebelli
- The sigmoid sinus drains into the internal jugular vein
What clinical syndrome results from injury to the mammillary bodies?
Wernicke-Korsakoff Syndrome - lesions to the anterior nucleus result in memory impairment.
What is the distinguishing feature of a lateral pontine syndrome that indicates that the occlusion is in the anterior inferior cerebellar artery (AICA)?
Anterior inferior cerebellar artery (AICA) supplies the lateral pons and middle and inferior cerebellar peduncles
Cochlear nucles - supplied by the AICA
Structures within the pons supplied by the pontine arteries and AICA:
- Facial (CN VII) nerve and nucleus
- Vestibular nuclei (CN VIII)
- Trigeminal (CN V) nuclei and nerve
- Spinal trigeminal tract
- Inferior and middle cerebellar peduncles
Other structures within the pons supplied only by pontine arteries:
- Abducens (CN VI) nucleus and nerve
- Corticospinal fibers
- Medial lemniscus
- Medial longitudinal fasiculus
Occlusion of the AICA can result in lateral pontine syndrome:
- Ipsilateral facial paralysis
- Ipsilateral hearing loss due to ipsilateral cochlear nucleus damage
- Vestibular signs (e.g. vertigo, nystagmus) due to ipsilateral vestibular nucleus damage
- Ipsilateral loss of facial pain and temperature sensation
- Ipsilateral ataxia
What arteries supply the circle of Willis?
The brain receives its blood supply from the carotid arteries and the vertebrobasilar system.
What are three possible sequelae of middle cerebral artery occlusion?
The MCA supplies the lateral portion of the cerebral hemisphere including Broca’s area, Wernicke’s area and motor sensory cortices of the contralateral trunk-arm-face
- Lenticulostriate arteries are penetrating branches of the MCA supply the internal capsule and structures of the basal ganglia
- Very frequently involved in lacunar strokes
Occlusion of the MCA can result in:
- Paralysis/sensory loss of contralateral face and arm
- Broca’s and Wernicke’s aphasia
- Contralateral neglect syndrome
Where are the locations of the nuclei of cranial nerve 5?
- There are 4 primary nuclei within the trigeminal system: the main sensory nucleus, the spinal nucleus, the mesencephalic nucleus and the motor nucleus
- The mesencephalic nucleus ==> lateral portions of the midbrain and superior pons
- Main sensory nucleus ==> lateral pons, immediately caudal to the mesencephalic nucleus
- Motor nucleus ==> pons, medial to the main sensory nucelus
- Spinal nucleus ==> long collection of nerve bodies and fibers, begins at the junction of the pons and medulla, caudal to the main sensory nucleus, stretches to the level of C2 or C3 within the spinal cord.
What are the arteries of the vertebrobasilar system?
- Subclavian arteries ==> vertebrobasilar system (vertebral arteries) which become the posterior cerebral arteries (PCA)
- After giving off the posterior spinal artery (PSA), posterior inferior cerebellar arteries (PICA) and anterior spinal artery (ASA), the vertebral arteries fuse to form the basilar artery
- The basilar artery runs along the centre of the anterior/ventral pons. It’s branches are:
- AICA
- Multiple pontine arteries
- Superior cerebellar arteries
- Posterior communicating artery connecting PCA to the internal carotid and circle of Willis ==> supplies the hypothalamus and ventral thalamus
- Posterior communicating artery ==> second most common location of aneurysm in circle of Willis ==> results in third nerve palsy due to compression of CN III
- Occlusion of the BASILAR ARTERY results in ‘‘Locked-In Syndrome’’.
Where is CSF produced?
- Choroid plexus is responsible for the production of CSF
- The third ventricle communicates with the fourth ventricle via the cerebral aqueduct which when obstructed causes a non-communicating hydrocephalus.
- A lesion to the optic tract will cause a contralateral homonymous hemianopsia.
What are the branches of the basilar artery as it runs along the pons?
The basilar artery runs along the center of the anterior/ventral pons. Its branches are:
Anterior inferior cerebellar arteries (AICA)
Multiple pontine arteries
Superior cerebellar artery
What is the pathway of the jaw-jerk reflex?
It is a reflex of the trigeminal system:
Tapping the chin of a patient activates the jaw-jerk reflex:
Pathway: V3 ==> mesencephalic nucleus of V ==. motor nucleus of V ==> masseter
Name a pathology associated with the following structure:
Putamen
Posterior limb of the internal capsule
The putamen is the most common site of a hypertensive bleed in the central nervous system
Atrophy of the caudate nucleus is seen in Huntington’s disease
A lesion to the posterior limb of the internal capsule results in contralateral loss of all conscious somatosensation and contralateral hemiparesis of the body and face
What is the structure of the lateral ventricles? How do they communicate with the third ventricle?
- Within the ventricles CSF is produced and secreted by the ependymal cells of the vascular choroid plexus
- Each lateral ventricle has a central body as well as an anterior horn, posterior horn and inferior horn. They communicate with the third ventricle via the interventricular foramen of Monro
- The third ventricle is between the two halves of the diencephelon (thalamus and hypothalamus)
- It communicates with the fourth ventricle via the cerebral aqueduct
- Clincal correlate ==> congenital stenosis of the cerebral aqueduct can result in non-communicating hydrocephalus
- The fourth ventricle is within the brainstem - it is bordered ventrally by the pons and medulla and dorsally by the cerebellum. It communicates with the cisterna magna via two lateral foramina (of Luschka) and a medial foramen (of Magendie)
- The third ventricle is between the two halves of the diencephelon (thalamus and hypothalamus)
- Each lateral ventricle has a central body as well as an anterior horn, posterior horn and inferior horn. They communicate with the third ventricle via the interventricular foramen of Monro
What structures are supplied by the posterior communicating artery?
The posterior communicating artery connects the PCA to the internal carotid and circle of Willis. It supplies the hypothalamus and ventral thalamus.
Outline the auditory pathway.
The cochlear nerve CN VIII transmits auditory signals from the inner ear
First order neurons - the spiral ganglion contains bipolar cells that innervate hair cells within the organ of corti - their axons make up CN VIII
CN VIII enters the brainstem at the CP angle, the synapses in cochlear nuclei
Second order neurons - decussating fibers from the ventral cochlear nuclei travel in the trapezoid body (within the pons) and synapse in the now contralateral superior olivary nucleus (note that most fibers decussate but some remain ipsilateral)
Third order neurons: Neuron cell bodies within the superior olivary nucleus send axons rostrally through the lateral lemniscus and synapse in the inferior colliculus
Fourth and fifth order neurons - neurons in the inferior colliculus project to the medial geniculate body of the thalamus. Neurons from the thalamus project to the auditory cortext within the transverse gyrus of the temporal lobe.
What structures are supplied by the middle cerebral artery?
The middle cerebral artery (MCA) supplies the lateral portion of the cerebral hemisphere, including Broca’s area, Wernicke’s area, and motor-sensory cortices of the contralateral trunk-arm-face.
