12Anatomy
A Neglect syndromes
Neglect syndromes and attentional deficits can occur with pulvinar nuclear lesions. The pulvinar nucleus is the largest nucleus in the thalamus; it is located most posteriorly, and is associated with visual pathways. (E) Memory difficulties may occur with lesions of the anterior nucleus of the thalamus, which is considered part of the limbic system.
C Rubro-olivary tract/central tegmental tract (triangle of Mollaret)
The triangle of Mollaret is a functional circuit connecting the dentate nucleus of the cerebellum to the contralateral red nucleus through the superior cerebellar peduncle, the red nucleus to the ipsilateral inferior olivary nucleus through the central tegmental tract, the inferior olivary nucleus to the contralateral cerebellar cortex through the inferior cerebellar peduncle, and the cerebellar cortex to the ipsilateral dentate nucleus. Lesions of the triangle of Mollaret produce palatal myoclonus, which is one of the few movement disorders that do not disappear during sleep. Palatal myoclonus appears in a delayed fashion following such lesions. Ocular myoclonus can accompany palatal myoclonus due to lesions in the central tegmental tract.
A Medial forebrain bundle
The medial forebrain bundle carries information from the ventral tegmental area to the nucleus accumbens in the ventral striatum. The nucleus accumbens also receives input from the hippocampus, amygdala, and prefrontal cortex with output to the ventral pallidum.
B Nucleus tractus solitarius
The nucleus tractus solitarius is a medullary nucleus also receiving afferents from chemoreceptors in the aortic and carotid bodies.
A Area postrema
The area postrema is located in the medulla and is the only paired circumventricular organ. (C) The nucleus prepositus hypoglossi is a medullary structure and neural integrator responsible for horizontal gaze control during smooth-pursuit eye movements. (D) The nucleus ambiguus is located in the lateral and rostral medulla and supplies the efferent motor fibers for the glossopharyngeal and vagus nerves. (E) The inferior salivary nucleus is a medullary structure responsible for the parasympathetic efferents to the parotid gland to induce salivation.
D Pacinian corpuscles
Pacinian corpuscles detect rapid vibrations and have peak sensitivity with vibrations around 250 Hz. They also are keen at detecting surface texture, which makes their localization in the skin ideal. Additionally, they are found in internal organs. (A) Ruffini endings are slowly adapting receptors found in subcutaneous tissues and respond to sustained pressure. (B) Meissner corpuscles are very sensitive to light touch and function best with vibrations less than 50 Hz. They rapidly adapt and are found in areas very sensitive to light touch, such as the finger pads. (C) Merkel disks occur in the superficial skin layers and mucosa, and provide information about pressure and texture. They are slowly adapting. (E) Free nerve endings are unencapsulated receptors in the skin that detect painful stimuli.
B Floor of the third ventricle
There is no choroid plexus along the floor of the third ventricle. Choroid plexus is present at the other locations and is responsible for the bulk of cerebrospinal fluid production. Cerebrospinal fluid is produced by bulk transependymal flow along the floor of the third ventricle.
C Sympathetic nerve that unites with the greater superficial petrosal nerve to form the Vidian nerve
The deep petrosal nerve emerges from the internal carotid plexus and traverses the carotid canal to join the superficial petrosal nerve to form the Vidian nerve (also known as the nerve of the pterygoid canal). The deep petrosal nerve carries the sympathetics that innervate the pterygopalatine ganglion.
D Deep peroneal nerve
The deep peroneal nerve innervates the tibialis anterior, extensor digitorum longus, extensor hallucis longus, extensor digitorum brevis, and extensor hallucis brevis, and provides cutaneous innervation to the webbing between the first and second toes. (A) The superficial peroneal nerve innervates the peroneus longus and brevis, and provides cutaneous innervation over the anterolateral leg and the dorsum of the foot, except for the first web space. (B) The medial dorsal cutaneous nerve divides into three branches, and provides sensation to the medial side of the hallux and adjacent sides of the second and third toes. (C) The intermediate dorsal cutaneous nerve divides into four branches, and supplies sensation to the medial and lateral sides of the third, fourth, and fifth toes. (E) The tibial nerve innervates the gastrocnemius, popliteus, soleus, and plantaris, and contributes to the sural nerve. It also innervates the tibialis posterior, flexor digitorum longus, flexor hallucis longus, sole of the foot, and posterior lower leg.
D Recurrent artery of Heubner
The recurrent artery of Heubner is the most proximal branch of the A2 segment distal to the anterior communicating artery. It runs in a retrograde fashion and enters the anterior perforating substance. (A) The tentorial artery is a branch of the meningohypophyseal trunk that runs posteriorly to supply blood to the tentorium. (B) The McConnell capsular artery/arteries arise from the medial trunk of the intracavernous internal carotid artery and supply blood to the pituitary gland. They are present in only 28% of the population. (C) The frontopolar artery is a branch of the A2 segment that supplies blood to the medial frontal lobe and the lateral surface of the superior frontal gyrus. (E) The medial lenticulostriate arteries arise from the A1 segment and supply blood to the globus pallidus and medial putamen.
E Periaqueductal gray matter
The periaqueductal gray matter suppresses and modulates pain in the descending pathways within the midbrain tegmentum. (A) The superior colliculus functions to modulate gaze shifts. (B) The substantia nigra contains high levels of dopamine, and the loss of neurons in the pars compacta region characterizes Parkinson disease. (C) The crus cerebri is the anterior white matter portion of the cerebral peduncle that contains the motor tracts. (D) The red nucleus controls tone and gait.
C Internal maxillary artery
Epistaxis after transsphenoidal surgery can be immediate or delayed. Injury to the internal carotid artery can cause life-threatening epistaxis, and pseudoaneurysm formation can lead to delayed hemorrhage, illustrating the need for an angiogram after suspected injury. In the external carotid system, the sphenopalatine artery, originating from the internal maxillary artery, is the most common branch injured during transsphenoidal surgeries. The artery is found in the inferolateral corner of the sphenoid ostium, and if it is injured, it can retract toward the maxilla and be difficult to coagulate.
B Spinal accessory nerve
The long thoracic nerve provides innervation to the serratus anterior and is the most common cause of scapular winging. Its origin is the C5–C7 nerve roots. The dorsal scapular nerve (arising from the C5 root) innervates the rhomboids and levator scapulae. The spinal accessory nerve innervates the trapezius and sternocleidomastoid. Injury to any of these three nerves can cause a winged scapula. (A) The suprascapular nerve innervates the supraspinatus and infraspinatus. It is a branch of the upper trunk of the brachial plexus. (C) The thoracodorsal nerve emerges from the posterior cord and innervates the latissimus dorsi. (D) The lateral thoracic nerve does not exist.
B Spinal dura
C C
C is the location of the lateral component of the spinothalamic tracts. (A) A is the location of the dorsal columns. (B) B is the location of the anterior portion of the corticospinal tracts. (D) D is the location of the lateral corticospinal tracts. (E) E is the location of the reticulospinal tracts.
A Along the midline surface of the cerebral hemisphere just anterior to the primary motor cortex leg area
Injury or irritation of the supplementary motor area produces a paucity of volitional movements along with a contralateral hemineglect and apraxias. Typically these symptoms resolve in a week or two when they are due to supplementary motor area damage, whereas the symptoms tend to be long standing when they are due to damage of the motor cortex. (B) The secondary somatosensory area is found in the parietal operculum. (C) The premotor cortex is in Brodmann area 6 on the lateral surface of the cerebral hemisphere. The medical extension of this area is the supplementary motor area. (D) The Broca area is within the pars opercularis and pars triangularis of the inferior frontal gyrus. (E) The paracentral lobule of the parietal lobule lies along the medial surface of the cerebral hemisphere and is continuous with the postcentral gyrus of the parietal lobe. The anterior component of this (the medial surface of the precentral gyrus) is the supplementary motor area.
C Chorda tympani
The petrotympanic fissure is located between the temporomandibular joint and the middle ear to enable communication between these structures. It opens just anterior and superior to the tympanic membrane, and houses the anterior malleus ligament, anterior tympanic branch of the internal maxillary artery, and chorda tympani. (A) The pterygoid artery is a branch of the second part of the internal maxillary artery and supplies blood to the medial and lateral pterygoid muscles. (B) The posterior deep temporal artery is a branch of the second part of the internal maxillary artery and supplies blood to the temporalis muscle. (D) The chorda tympani does not join with the lingual nerve until after it emerges from the skull through the infratemporal fossa. (E) The greater superficial petrosal nerve travels over the surface of the foramen lacerum and joins the deep petrosal nerve to form the nerve of the pterygoid canal (Vidian nerve).
A Frontal bone
The orbit is made up of seven bones: pars orbitalis of the frontal, lacrimal, lamina papyracea of the ethmoid, zygomatic, maxillary, palatine, and greater and lesser wings of the sphenoid. The nasal septum is composed of five bones and structures: perpendicular plate of the ethmoid, vomer, septum cartilage, maxillary, and palatine.
A Abductor pollicis brevis
The median nerve originates from the C5-T1 roots. In the hand, the median nerve innervates the “LOAF” muscles (lumbricals 1 and 2, opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis). The ulnar nerve innervates the opponens digiti minimi, flexor digiti minimi brevis, abductor digiti minimi, lumbricals 3 and 4, interossei, and adductor pollicis. The radial nerve innervates the extensors (digitorum, digiti minimi, carpi ulnaris, pollicis brevis, pollicis longus, and pollicis indicis) as well as the abductor pollicis longus.
A Ectoderm
The pituitary is derived from the dual ectoderm. Around day 28 of embryogenesis, the Rathke pouch arises from a diverticulum from the stomodeum, which is derived from the ectoderm. The infundibulum arises from the neuroectoderm and grows inferiorly, where it eventually contacts the Rathke pouch. By the fifth week of embryogenesis, the neck of the Rathke pouch contacts the infundibulum and separates from the oral epithelium. The residual lumen of the Rathke pouch narrows to form a cleft and regresses. Persistence of the pouch is considered to be the cause of a Rathke cleft cyst.
E Calcarine sulcus
The cuneus (Brodmann area 17) is the primary visual cortex and is bounded anteriorly by the parieto-occipital sulcus and inferiorly by the calcarine sulcus. (C) The lingual gyrus lies between the calcarine sulcus and posterior part of the collateral sulcus and contributes to Brodmann area 19. (D) The collateral eminence is found in the lateral aspect of the occipital horn and is a result of invagination of the collateral sulcus.
A Fornix, tela choroidea, velum interpositum, tela choroidea, and choroid plexus
The tela choroidea is composed of pia that sits on the velum interpositum (the potential space containing the internal cerebral veins). Failure of closure of the posterior end of this potential space results in a cavum velum interpositum that communicates with the quadrigeminal cistern.
B Inferior petrosal sinus
The inferior petrosal sinus drains into the sigmoid sinus/jugular vein. (A) The superior petrosal sinus runs along edge of the tentorium and drains into the transverse sinus. (C) The vein of Labbé is a superficial vein that anastomoses the middle cerebral vein with the transverse sinus. (D) The basal vein of Rosenthal begins in the anterior perforated substance and receives contributions from the anterior cerebral vein, deep sylvian vein, and inferior striate veins. The basal vein of Rosenthal then passes around the cerebral peduncle to drain blood into the vein of Galen. (E) The straight sinus is the union of the vein of Galen and inferior sagittal sinus and drains into the torcular/transverse sinus.
B Middle cerebellar peduncle
Corticopontine fibers project through the middle cerebellar peduncle (brachium pontis) along pontocerebellar fibers. (A) The inferior cerebellar peduncle (restiform and juxtarestiform bodies) receives signals from the spinocerebellar tract, olivary nucleus, and vestibular nuclei. (C) Most fibers emerging from the cerebellum do so through the superior cerebellar peduncle (brachium conjunctivum) and then synapse on the red nucleus or motor nuclei of the thalamus.
E Cingulate gyrus
The medial limbic circuit also is known as the Papez circuit. It essentially is the limbic system circuitry. The Papez circuit begins in the hippocampus (subiculum) and then projects to the fornix followed by the mammillary bodies. The mammillary bodies project along the mammillothalamic tract to the anterior thalamic nucleus and then to the cingulum followed by the entorhinal cortex. The circuit is completed as the entorhinal cortex projects back to the hippocampus.
C Anterior to and between the anterior and posterior cerebellar lobes
The flocculonodular lobe is part of the vestibulocerebellum and is involved with maintenance of posture. (A) The anterior lobe is rostral to the primary fissure. (B) The posterior lobe is caudal to the primary fissure. (D) The vermis is located in a midsagittal position. (E) The tectum of the midbrain is rostral to the anterior lobe and posterior to the sylvian aqueduct.
C Globus pallidus
The globus pallidus sends afferents to the subthalamic nucleus, which also receives fewer afferents from the substantia nigra pars compacta and pedunculopontine nucleus.
A Anterior divisions of the upper and middle trunks
The lateral cord is derived from the anterior divisions of the superior and middle trunks. (C) The posterior cord is formed from the posterior divisions of the superior, middle, and inferior trunks. (D) The medial cord is formed from the anterior division of the inferior trunk.
A Areas 1, 2, and 3
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