Block 5 Neuro Atlas Ch 4 W Expl

1. A lumbar puncture, commonly called a "lumbar tap, "consists of a needle being inserted through an intervertebral space into the lumbar cistern to retrieve a sample of cerebrospinal fluid. Which of the following is the most likely level for the insertion of this needle?

L1–L2

L2–L3

L4–L5

S1–S2

T12–L1

The L4–L5 interspace is commonly used for a lumbar puncture. The L3–L4 space may also be used. Levels T12 toL2–L3 are too high. Because the caudal end of the spinal cord(the conus medullaris) may be as low as L2 in some individuals, levels T12–L1 to L2–L3 are not used, as this would most likely result in damage to the spinal cord. The S1–S2 vertebrae are fused so there is no intervertebral space through which a needle can pass. Furthermore, the dural sac ends at about S2.(p.12,53)

Explanation

The L4–L5 interspace is commonly used for a lumbar puncture. The L3–L4 space may also be used. Levels T12 toL2–L3 are too high. Because the caudal end of the spinal cord(the conus medullaris) may be as low as L2 in some individuals, levels T12–L1 to L2–L3 are not used, as this would most likely result in damage to the spinal cord. The S1–S2 vertebrae are fused so there is no intervertebral space through which a needle can pass. Furthermore, the dural sac ends at about S2.(p.12,53)

2. Which of the following portions of the ventricular system does not contain choroid plexus?

Cerebral aqueduct

Fourth ventricle

Lateral ventricle

Interventricular foramen

Third ventricle

The cerebral aqueduct does not contain choroid plexus. The choroid plexus in the lateral ventricle is continuous from the inferior horn into the atrium and into the body of the ventricle, and through the interventricular foramen with the choroid plexus located along the roof of the third ventricle. There is a tuft of choroid plexus in the fourth ventricle, a small part of which extends into the lateral recess and through the lateral foramen (of Luschka) into the subarachnoid space at the cerebellopontine angle.(p.53,57)

Explanation

The cerebral aqueduct does not contain choroid plexus. The choroid plexus in the lateral ventricle is continuous from the inferior horn into the atrium and into the body of the ventricle, and through the interventricular foramen with the choroid plexus located along the roof of the third ventricle. There is a tuft of choroid plexus in the fourth ventricle, a small part of which extends into the lateral recess and through the lateral foramen (of Luschka) into the subarachnoid space at the cerebellopontine angle.(p.53,57)

3. A 20-year-old man is transported from the site of a motorcycle collision to the emergency department. Upon arrival he is unconscious, but awakens and is quite lucid; he remembers his name, address, dog's name, and his phone number. He is admit-ted to the hospital for observation but rapidly deteriorates and dies. This is sometimes called "talk and die. "This man most likely suffered which of the following?

Acute bacterial meningitis

Concussion

Epidural hemorrhage

Subarachnoid hemorrhage

Subdural hemorrhage

The sequence of unconsciousness, lucidity, rapid deterioration, and death may be seen in patients with head trauma with epidural hemorrhage. These patients, during the lucid interval, may seem quite coherent but then suddenly deteriorate. Acute bacterial meningitis may develop suddenly, but would be characterized by fever, confusion, and stupor. In many cases, concussion is a mild injury that causes temporary confusion and memory impairment that typically resolves within minutes to hours. Subarachnoid and subdural hemorrhage may be seen in head trauma, but the signs and symptoms are different and these patients do not usually go through the “talk and die “sequence.(p.52)

Explanation

The sequence of unconsciousness, lucidity, rapid deterioration, and death may be seen in patients with head trauma with epidural hemorrhage. These patients, during the lucid interval, may seem quite coherent but then suddenly deteriorate. Acute bacterial meningitis may develop suddenly, but would be characterized by fever, confusion, and stupor. In many cases, concussion is a mild injury that causes temporary confusion and memory impairment that typically resolves within minutes to hours. Subarachnoid and subdural hemorrhage may be seen in head trauma, but the signs and symptoms are different and these patients do not usually go through the “talk and die “sequence.(p.52)

4. What is the most likely cause of spontaneous subarachnoid hemorrhage?

Bleeding from an astrocytoma

Bleeding from a meningioma

Blood from an arteriovenous malformation

Rupture of an aneurysm

Trauma to the head and brain

The most common cause of blood in the subarachnoid space is trauma. The most common cause of spontaneous(also commonly called nontraumatic) subarachnoid hemorrhage is the rupture of an intracranial aneurysm. Brain tumors or AVMs may bleed but these are not major sources of extravasated intracranial blood.(p.52,54)

Explanation

The most common cause of blood in the subarachnoid space is trauma. The most common cause of spontaneous(also commonly called nontraumatic) subarachnoid hemorrhage is the rupture of an intracranial aneurysm. Brain tumors or AVMs may bleed but these are not major sources of extravasated intracranial blood.(p.52,54)

5. Tumors of the choroid plexus are most commonly seen inpatients in which of the following age ranges?

Birth to 2 years of age

4–8 years of age

10–15 years of age

17–23 years of age

25years of age

Tumors of the choroid plexus are most commonly seen (about 70% of cases) in patients less than 2 years of age. In younger patients these lesions are more often located supratentorially; when they occur in older patients they are frequently infratentorial. These lesions may grow relatively rapid.(p.62–63)

Explanation

Tumors of the choroid plexus are most commonly seen (about 70% of cases) in patients less than 2 years of age. In younger patients these lesions are more often located supratentorially; when they occur in older patients they are frequently infratentorial. These lesions may grow relatively rapid.(p.62–63)

6. A 20-year-old man is brought to the emergency department from the site of a motorcycle accident. He is unconscious and has a broken femur, humerus, and extensive facial injuries. Axial CT shows a white layer on the lateral aspect of the left hemisphere that is approximately 5 mm thick and extends for12 cm. This observation most likely represents:

Epidural hemorrhage/hematoma

Parenchymatous hemorrhage in the cortex

Subarachnoid hemorrhage

Subdural hemorrhage/hematoma

Ventricular hemorrhage

Trauma may cause epidural hemorrhage, subdural hemorrhage, or subarachnoid hemorrhage. Acute subdural hemorrhage/hematoma appears white (hyperdense) on the CT and usually presents as a comparatively thin but long defect. Epidural hemorrhage usually is seen as a shorter but thicker lesion and may appear loculated (have some sort of internal structure).The structure (shape) of this lesion does not con-form to hemorrhage into the substance of the brain (brain parenchyma),into the subarachnoid space (or cisterns),and certainly not to hemorrhage into the ventricles.(p.52,54,57)

Explanation

Trauma may cause epidural hemorrhage, subdural hemorrhage, or subarachnoid hemorrhage. Acute subdural hemorrhage/hematoma appears white (hyperdense) on the CT and usually presents as a comparatively thin but long defect. Epidural hemorrhage usually is seen as a shorter but thicker lesion and may appear loculated (have some sort of internal structure).The structure (shape) of this lesion does not con-form to hemorrhage into the substance of the brain (brain parenchyma),into the subarachnoid space (or cisterns),and certainly not to hemorrhage into the ventricles.(p.52,54,57)

7. A 29-year-old woman becomes acutely ill with high fever, a stiff neck, and stupor. A lumbar puncture reveals cloudy cerebrospinal fluid from which organisms are cultured. Which of the following organisms were most likely revealed in this patient?

Escherichia coli

Haemophilus influenzae

Herpes simplex

Listeria monocytogenes

Streptococcus pneumoniae

Approximately one-half of cases of bacterial meningitis in adults are caused by S. pneumoniae. E. coli
and L.monocytogenes are causative agents in neonates and children, although the latter (L. monocytogenes) is present in less than10% of cases. Although H. influenza was a major cause of bacterial meningitis in children, the use of a vaccine has reduced this bacterium as a causative agent to well under 10% of cases. H. simplex is a virus.(p.52)

Explanation

Approximately one-half of cases of bacterial meningitis in adults are caused by S. pneumoniae. E. coli
and L.monocytogenes are causative agents in neonates and children, although the latter (L. monocytogenes) is present in less than10% of cases. Although H. influenza was a major cause of bacterial meningitis in children, the use of a vaccine has reduced this bacterium as a causative agent to well under 10% of cases. H. simplex is a virus.(p.52)

8. A 79-year-old man is brought to the emergency department by his wife. He is lethargic, complains of an absolutely horrible(thunderclap) headache, and is nauseated. The wife explains that her husband was painting the bathroom door when he got sick. This man most likely suffered which of the following?

Acute bacterial meningitis

Epidural hemorrhage

Subarachnoid hemorrhage

Subdural hemorrhage

Viral meningitis

The occurrence of a sudden, explosive, and severe headache is characteristic of subarachnoid hemorrhage resulting from aneurysmal rupture. The severe sudden pain is due to the rapid change in pressure between the arterial system and the low-pressure environment of the CSF-filled subarachnoid space. Meningitis, even acute bacterial, may be slow in onset and associated with lethargy, confusion, and fever. Epidural and subdural hemorrhages, even in older patients, are usually precipitated by a causative event such as a fall or automobile collision; this was not the case in this patient.(p.52,57)

Explanation

The occurrence of a sudden, explosive, and severe headache is characteristic of subarachnoid hemorrhage resulting from aneurysmal rupture. The severe sudden pain is due to the rapid change in pressure between the arterial system and the low-pressure environment of the CSF-filled subarachnoid space. Meningitis, even acute bacterial, may be slow in onset and associated with lethargy, confusion, and fever. Epidural and subdural hemorrhages, even in older patients, are usually precipitated by a causative event such as a fall or automobile collision; this was not the case in this patient.(p.52,57)

9. Which of the following represents the most common cause of blood in the subarachnoid space (subarachnoid hemorrhage)?

Bleeding from an arteriovenous malformation

Bleeding from a meningioma

Bleeding from a tumor

Rupture of an aneurysm

Trauma to the head and brain

Trauma is the most common cause of subarachnoid hemorrhage (SAH).The most common cause of spontaneous(also called nontraumatic) SAH is bleeding from a ruptured aneurysm (about 75% of all spontaneous cases).Bleeding from an arteriovenous malformation (AVM) is an infrequent cause of SAH (about 5% of cases),and bleeding from brain tumors into the subarachnoid space is rare. Meningiomas are usually slow-growing tumors that may have a rich vascular supply but rarely hemorrhage spontaneously.(p.52)

Explanation

Trauma is the most common cause of subarachnoid hemorrhage (SAH).The most common cause of spontaneous(also called nontraumatic) SAH is bleeding from a ruptured aneurysm (about 75% of all spontaneous cases).Bleeding from an arteriovenous malformation (AVM) is an infrequent cause of SAH (about 5% of cases),and bleeding from brain tumors into the subarachnoid space is rare. Meningiomas are usually slow-growing tumors that may have a rich vascular supply but rarely hemorrhage spontaneously.(p.52)

10. The CT of a 77-year-old man shows a calcified tuft of choroid plexus, the glomus choroideum. Which of the following represents the location of this part of the choroid plexus?

Anterior horn of the lateral ventricle

Atrium of the lateral ventricle

Body of the lateral ventricle

Caudal roof of the third ventricle

Temporal horn of the lateral ventricle

The glomus choroideum is found in the atrium of the lateral ventricle. This part of the choroid plexus is rostrally continuous with that in the body of the lateral ventricle and continuous anteroinferiorly with that in the temporal horn. The roof of the third ventricle has a small portion of choroid plexus that is continuous with that in the body of the ventricle
via the interventricular foramen. The anterior horn contains no choroid plexus.(p.5)

Explanation

The glomus choroideum is found in the atrium of the lateral ventricle. This part of the choroid plexus is rostrally continuous with that in the body of the lateral ventricle and continuous anteroinferiorly with that in the temporal horn. The roof of the third ventricle has a small portion of choroid plexus that is continuous with that in the body of the ventricle
via the interventricular foramen. The anterior horn contains no choroid plexus.(p.5)

11. The abducens nerve exits the brainstem at the pons-medulla junction generally in line with the preolivary sulcus and passes rostrally just lateral to, and in the same cistern as, the basilar artery. En route the abducens nerve passes through which of the following cisterns?

Ambient

Inferior cerebellopontine

Premedullary

Prepontine

Superior cerebellopontine

The prepontine cistern is located external to the basilar pons and contains the abducens nerve, basilar artery, origin of the anterior inferior cerebellar artery, and small perforating arteries and veins. The ambient cistern is located on the lateral aspect of the midbrain and contains the trochlear nerve and several major arteries. The premedullary cistern is located at the anterior surface of the medulla and contains the anterior spinal artery. The inferior cerebellopontine cistern contains the glossopharyngeal, vagus, and accessory nerves. The superior cerebellopontine cistern contains the trigeminal, facial, and vestibulocochlear nerves plus a short segment of the trochlear nerve.(p.56–58)

Explanation

The prepontine cistern is located external to the basilar pons and contains the abducens nerve, basilar artery, origin of the anterior inferior cerebellar artery, and small perforating arteries and veins. The ambient cistern is located on the lateral aspect of the midbrain and contains the trochlear nerve and several major arteries. The premedullary cistern is located at the anterior surface of the medulla and contains the anterior spinal artery. The inferior cerebellopontine cistern contains the glossopharyngeal, vagus, and accessory nerves. The superior cerebellopontine cistern contains the trigeminal, facial, and vestibulocochlear nerves plus a short segment of the trochlear nerve.(p.56–58)

12. The mother of a 30-month-old girl brings her daughter to the pediatric clinic. The mother explains that her daughter has been crying incessantly, complaining that her head and stomach "hurt, "and has thrown up several times over the last 3weeks.The mother says she thinks it is getting worse. CT reveals a tumor in the roof of the third ventricle. Further evaluation confirms that it is a choroid plexus papilloma. Which of the following vessels is the main source of blood to this tumor?

Anterior choroidal artery

Anterior inferior cerebellar artery

Lateral posterior choroidal artery

Medial posterior choroidal artery

Superior cerebellar artery

The medial posterior choroidal artery is the main blood supply to the choroid plexus (CP) in the roof of the third ventricle and the source of the blood in the ventricle in the patient. The CP in the temporal horn is served by the anteriorchoroidal artery and the CP in the atrium and body of the lateral ventricle is served by the lateral posterior choroidal artery. The tuft of CP sticking out of the foramen of Luschka is served by the anterior inferior cerebellar artery. The superior cerebellar artery does not provide blood supply to any portion of the choroid plexus.(p.58,62–63)

Explanation

The medial posterior choroidal artery is the main blood supply to the choroid plexus (CP) in the roof of the third ventricle and the source of the blood in the ventricle in the patient. The CP in the temporal horn is served by the anteriorchoroidal artery and the CP in the atrium and body of the lateral ventricle is served by the lateral posterior choroidal artery. The tuft of CP sticking out of the foramen of Luschka is served by the anterior inferior cerebellar artery. The superior cerebellar artery does not provide blood supply to any portion of the choroid plexus.(p.58,62–63)