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Cranium, Ventricles and Meninges


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Where are the foramen magnum and the cervicomedullary junction?
At the base of the skull. The foramen magnum is the big hole (hence the name) at the base of the skull where the spine enters and becomes the brainstem. The cervico-medullary junction is the point where the spine becomes the brain stem (C-1 and the medulla oblongata).
Name the three cranial fossae and their locations.
Anterior-frontal lobe, separated from middle fossa by lesser wing of the sphenoid bone. Middle-temporal lobe, separate from posterior fossa by the petrous ridge of temporal bone (and a sheet of meninges). Posterior-contains the cerebellum and brainstem. (A.M.P.)
What are the meninges and what do they do?
Think P.A.D.
Pia mater is closest to the brain and spinal cord surfaces. It is highly vascular and closely adheres to the surface of the brain and spinal cord.
Arachnoid mater-think spiderweb, between the pia and the dura, adheres to the surface of the dura and is the space in which CSF "percolates" through the ventricular circulatory system.
Dura=Hard mater=mother-consists of 2 fibrous layers which are fused to each other and adhere to the inner surface of the skull except in 2 places where one layer dips inward: a. the falx cerebri (dura suspended from the roof of the cranium that separates the two hemispheres; b. the tentorium cerebelli-the tent like covering of the upper surface of the cerebellum. Supratentorial=above the tentorium and infratentorial is below the tentorium.
What are the three spaces formed by the meninges and what blood vessels can be found there?
Epidural: b/w inner surface of skull and dura. The Middle Meningeal Artery (MMA) is a branch of the external carotid artery and supplies the dura.
Subdural: b/w dura and arachnoid. Bridging veins and dural venous sinuses-provide venous drainage from brain and meninges.
Subarachnoid: b/w arachnoid and pia. CSF is here and the major arteries.
What structures produce cerebrospinal fluid?
The choroid plexus is the structure that produces CSF within the ventricular system.
Name the 3 spaces formed by the meninges.
Epidural, Subdural and Subarachnoid. Epidural is between the inner surface of the skull and the dura. The Middle meningeal artery is found here. Subdural is between the dura and the arachnoid. Bridging veins and dural venous sinuses provide venous drainage from the brain and meninges. Subarachnoid space is between arachnoid and pia. CSF and Major arteries before they penetrate the brain.
What meningeal layers envelope the spinal cord?
The same three that cover the brain-Pia, arachnoid and dura.
What structure produces CSF and where can it be found?
The choroid plexus is inside the ventricles and is a vascular structure that is lined with epithelial cells.
What type of cells line the inner walls of the ventricles?
Ependymal cells
Name the aspects of the lateral ventricles that identify their location within the cerebral hemispheres.
Frontal (anterior) Horns-extend anteriorly into the frontal lobe.
Occipital (posterior) Horns-extend back into the occipital lobe.
Temporal (Inferior) Horns-extend inferiorly and anteriorly into the temporal lobes.
The lateral ventricles communicate with the third ventricle via what structure?
The interventricular foramen of Monro.
The third ventricle is bounded by the thalamus and hypothalamus and connects with the fourth ventricle via what structure?
the cerebral aqueduct or the aqueduct of Sylvius, which travels through the midbrain.
The roof of the fourth ventricle is formed by what structure? and the floor is formed by?
the cerebellum. the pons and medulla.
Describe the circulation of CSF leaving the fourth ventricle.
CSF leave via the lateral foramina of Luschka and the midline foramen of Magendie, it travels around the brain and spinal cord in the subarachnoid space. It is reabsorbed by arachnoid granulations into the dural venous sinuses (back into the bloodstream).
What term is used to describe the widening of subarachnoid space to allow large CSF collections?
cistern-usually the label before this term identifies its placement.
The Blood Brain Barrier is known for what type of cells?
Endothelial cells. They have tight junctures. Brain capillary endothelial cells are so tightly fenestrated that cell transport is required for passage of water soluble substances. Systemic capillary cells are notable for a capillary wall separated by clefts allowing passage of fluids and molecules. Choroid epithelial cells form the blood/CSF barrier and the barrier between capillaries and CSF.
Blood-brain and blood-CSF barriers separate arterial blood from what?
the brain parenchyma. Although, lipid soluble substances cross both (such as Oxygen and Carbon Dioxide). Other substances are conveyed in both directions through transport systems.
What is the primary role of the Blood Brain Barrier?
To protect brain function from fluctuations in blood chemistry.
What structures allow the brain to respond to changes and secrete neuropeptides into the system?
Circumventricular organs.
Disruption of the BBB can be caused by tumor or infectious processes. Name some signs that the BBB has been breached.
Vasogenic edema-excessive extracellular fluid
Cytotoxic edema-excessive intracellular fluid within brain cells caused by cellular damage.
Since there are no pain receptors in brain parenchyma, how is headache pain caused?
Headache pain is usually the result of mechanical traction, inflammation or irritation of other structures in the head that are innervated, such as blood vessels, meninges, scalp and skull. *Although the side of the headache often corresponds to the side of pathology, this is not always the case.
Name possible triggers for a vascular headache.
Possible triggers for a vascular headache may include: Foods, stress, eye strain, menustrual cycle, and changes in sleep.
Vascular headache pain is throbbing and can be exacerbated by what?
Light, sound or sudden movement.
True or False: Vascular headache runs in the family.
True. 75% of sufferers have a family history of vascular headache/migraine.
Auras for migraines typically affect what sensory system?
Vision. There may be visual blurring, shimmereing, scintillating distortions, fortification scotoma (region of visual loss bordered by zigzagging lines resembling walls of a fort.
How long do vascular headaches typically last and how often do they occur?
These headaches may last from 30 minutes to 24 hours with some relief after sleeping. They may occur once very few years or several times a week.
Complicated migraine is often accompanied by transient focal neurologic deficits in what modalities?
These headaches may manifest with sensory phenomena, motor deficits and/or visual loss. The diagnosis of complicated migraine should be exclusionary, i.e. after other causes (post-ictal headache/ cerebrovascular diseases) have been ruled out.
Migraines have been treated acutely with NSAIDS, anti-emetics, serotonin agonists, ergot derivatives and rest in the dark, what preventive measures can be taken?
Patients may avoid these headaches by avoiding identified triggers, taking medications prophylactically, and improving hydration.
True or False: the cluster headache is as common ast the migraine.
False. The cluster headache is less than 1/10 as common as the migraine.
How often do cluster headaches occur?
They may occur once to several times per day over a few weeks then vanish for months.
There may be unilateral autonomic symptoms accompanying these headaches. Describe some of these symptoms and the type of pain associated with cluster headaches.
Symptoms may include tearing, eye redness, horners syndrom (ptosis, miosis, anhidrosis), unilateral flushing, sweating and nasal congestion.
Many of the treatments for cluster headache are similar to those for vacular headaches, what else has been effective?
Inhalation of oxygen has been effective in stopping an attack.
Tension type headaches are known for what type of pain and contraction of what?
These headaches have a steady dull ache (band-like sensation) which may be the consequence of excessive contraction of scalp and neck muscles.
Name some of the qualities of the tension-type headache.
steady dull ache, mild to moderate headache lasting few hours (there is a chronic form), treatment may consist of muscle relaxation techniques, NSAIDS, other analgesics and TCAs.
Other causes of headache:
subarachnoid hemorrhage, cerebral ischemia and infarction, post-ictus, low CSF, Increased CSF, Meningitis, pseudotumor cerebri, temporal arteritis. (see Table 5.2 for other causes of headache)
An intracranial mass is anything abnormal that occupies volume within the cranial vault (e.g., tumor, hemorrhage, abscess). What causes neurologic symptoms when a mass is present?
Compression and destruction of adjacent brain regions, local tissue, and blood vessels. 2, Increased intracranial pressure. 3. Herniation:mass effect and effacement. Disruption of the BBB leads to vasogenic edema. Compression of the ventricular system obstructs CSF flow resulting in hydrocephalus. Production of abnormal electrical activity=seizures, and midline shift, a shift away from the lesion. (pineal calcifications are used to measure exten of shift at the level of the upper brainstem and displacement and stretching of the upper brainstem impairs the RAS.
What are some signs and symptoms of Inreased Intracranial pressure?
Headache-worse in the AM because brain edema rises overnight from lying down.
Altered Mental Status-most important indicator-irritability and depressed level of alertness and attention.
Nausea and projectile vomiting.
Papilledema-engorgement and elevation of optic disc; sometimes also see retinal hemorrhage.
Visual loss caused by transient or permanent optic nerve damage.
Diplopia caused by traction on CN VI, causing unilateral or bilateral abducens nerve palsies. and Cushing's triad.
Treatment Goals for increased ICP are...?
Reduce to a safe level, giving time to treat underlying disorder.
Measure through LP, but do not perform if severely elevated ICP because of risk for herniation.
Uncal herniation or transtentorial herniation occurs where?
herniation of the medial temporal lobe, especially the uncus occurs inferiorly through the tentorial notch.
What are the symptoms of uncal herniation?
Blown pupil (compression of CNIII)ipsilateral to the lesion in 85% of the cases.
Hemiplegia-due to compression of cerebral peduncles and can be ipsilateral or contralateral to the lesion.
Coma-distortion of midbrain reticular formation.
What do you see with Central herniation?
Downward displacement of the brainstem or cerebellar tonsils through the foramen magnum.
A subfalcine herniation looks like what?
the cingulate gyrus and other brain structures have herniated under the falx cerebri to the other side of the cranium. There are no clinical signs, it may cause occlusion of the anterior cerebral arteries.
With a mild TBI, or concussion, is recovery usually complete?
Yes, however, one can see postconcussive syndrome (headaches; lethargy; mental dullness) that lasts for months after the incident.
Permanent injury to the brain, after a severe TBI can be the result of what?
Diffuse axonal damage
petechial hemorrhages
intracranial hemorrhage
cerebral contusion
tissue injury from penetrating trauma
cerebral edema contributing to increased ICP.
An Epidural hematoma is found where?
btw the skull and the dura. It is caused by the rupture of the middle meningeal artery from the fracture of the temporal bone. There may be increased ICP, and the patient may have a lucid interval before lapsing into unconsciousness.
What are the features of a subdural hematoma?
It is occurring between the dura and the arachnoid. there are 2 types?Chronic-slowly oozing blood collects; headache; cognitive impairment; unsteady gait; focal neurologic signs. Acute-caused by high velocity impact injury.
A subarachnoid hematoma is defined how?
It is between the arachnoid and the pia. There are two causes, nontraumatic and traumatic. Nontraumatic has a sudden onset with severe headache, meningeal irritation, nuchal rigidity, cranial nerve findings, and neuro deficits. Risk factors such as hypertension, smoking, alcohol and anything causing a sudden increase in ICP.
Traumatic is the result of bleeding into the CSF from damaged blood vessels due to contusions/traumatic injury.
Bleeding that occurs between or within the parenchyma of the cerebral hemispheres, brainstem, cerbellum of spinal cord is called what?
Intracerebral or intraparenchymal hemorrhage.
A traumatic intracerebral hemorrhage is caused by what?
Contusions from skull ridges; coup/contrecoup injury; commonly frontal or temporal poles.
A nontraumatic hemorrhage is caused by what?
Hypertension, brain tumor and vascular malformations. Most common: small penetrating blood vessels in the basal ganglia; thalamus; cerebellum; pons.
Vascular malformations may occur in what blood vessels?
All three. AVM's or arteriovenous malformations are congenital abnormalities that result in a direct connection between artery and vein; a tangle of abnormal blood vessels. The hemorrhage is usually intraparenchymal and the patient may present with headache and/or seizure. The cavernous malformation is an abnormally dilated vascular cavity lined by only one layer of vascular endothelium. Capillary tenagiectasias are small regions of abnormally dilated capillaries which rarely give rise to hemorrhage. Venous angiomas are dilated veins, there are no associated clinical symptoms, but they are associated with cavernous malformations.
Hydrocephalus is the termed used to describe what condition?
Excess CSF within the cranium.
What are the causes of hydrocephalus?
Excess CSF production-this is rare, but may be seen with certain tumors (choroid plexus papilloma). Obstruction of the flow in ventricles or subarachnoid space. This is more common and usually occurs at narrow points in the CSF circulatory pathway. Decrease in reabsorption due to damage or clogging of arachnoid granulations.
Name the two types of hydrocephalus.
Communicating and Non-communicating. In Communicating hydrocephalus, there is impaired CSF reabsorption in the arachnoid granulations, obstruction of the flow of CSF in the subarachnoid space or excess CSF production. Non-communicating=obstruction of flow within the ventricular system.
Symptoms of hydrocephalus include:
Any and all of the symptoms of increased ICP-headache, nausea, vomiting, cognitive impairment, decreased vision etc. dilation the ventricles compresses descending white matter pathways from frontol lobes leading to magnetic gait (feet barely leave the floor) and incontinence.
In infants, the skull expands, leading to increased head circumference and a bulging anterior fontanelle.
There may also be abnormalities in eye movement, mild results in sixth nerve palsy (incomplete or slow abduction of eye in horizontal direction; sever H results in inward deviation of both eyes.
Types of treatment for hydrocephalus.
Extraventricular shunt-ventriculostomy, fluid from the lateral ventricles is drained to a bag outside the head. Ventriculoperitoneal shunt-shunt tube passed from lateral ventricle into peritoneal cavity of abdomen.
Third ventriculostomy-via endoscopy, blunt instrument performates floor of third ventricle to allow CSF to drain.
Signs of Normal Pressure Hydrocephalus (NPH)
Chronically dilated ventricles, measurement of CSF pressure is not elevated.
Clinical signs of NPH
Gait difficulties, urinary incontinence and mental decline (3 Ws: wet, wobbly and wacky) Another symptom not mentioned in the notes is that many times these individuals have bowel urgency. The need for a bathroom comes upon them quite suddenly.
Another term associated with hydrocephalus is hydrocephalus ex vacuo
This is a term to describe when there is excell CSF in a region where brain tissue was lost due to a stroke, surgery, atrophy, etc.
What are some common etiologies for hydrocephalus in children?
Neural tube defects (spina bifida/meyelomeningocele), Dandy-Walker Syndrome, Aqueductal stenosis, and Intraventricular Hemorrhage (commonly associated with Premature Birth).
In adults, the most common CNS tumor is what?
The glioblastoma, brain mets (arising from neoplasms elsewere in the body that spread to the brain).
In kids, what is/are the most common?
Astrocytoma, medulloblastoma and ependymoma. 70% occur in the posterior fossa and 30% are supratentorial. Tumors in the posterior fossa are likely to cause hydrocephalus through obstruction or compression of the fourth ventricle.
Tumors present in many ways. True or false: a seizure or focal symptom is the best indicator of a tumor.
False. While it is true that seizures or focal symptoms may indicate the location of a tumor, this is not always the case. Sometimes Headache is a symptom. All symptoms depend on the size, location and rate of tumor growth.
What differentiates a benign tumor from a malignant one?
Benign tumors do not infiltrate or disseminate through the nervous system. Malignant tumors, while possessing the potential to spread rarely spread outside the CNS.
Surgical resection of a tumor requires that how much be resected for there to be a positive effect on outcome?
> 90% tumor removal is required.
Name other treatments for primary CNS tumors.
Radiation therapy, Chemotherapy and steroids (to reduce edema).
Gliomas arise from what type of cell?
Glial cells-think oligodendroglioma. Gliomas are subdivided into several types, but share a common denominator-they come from glial cells.
Meningiomas are found where and arise from what?
In the meninges and arise from arachnoid villus cells.
Pituitary adenomas have what effect on the CNS?
They may cause endocrine disturbance and may cause a bitemporal field defect by compressing the optic chiasm.
Schwannomas are most commonly found where?
Cranial Nerve VIII.
If a person has advanced HIV-1 infection or is immunosuppressed, what is the most likely tumor to develop and where?
A lymphoma and they arise in areas adjacent to the ventricles.
A tumor in the pineal region is how common and what are its effects?
In fact they are quite uncommon, but when they do occur, they obstruct the cerebral aqueduct causing hydrocephalus and compression of the midbrain.
Of the three types of pediatric tumors mentioned, what are the prognoses?
Cerbellar astrocytoma: grade I/IV is often cured by surgery alone. The Medulloblastoma and the ependymoma often have a worse outcome. Growth is difficult to control.
Infectious meningitis develops from infection of the CSF in what area?
The subarachnoid space.
Symptoms of meningitis include what?
(on imaging) meningeal irritation, (clinically)headache, lethargy, photophobia, phonophobia, fever, nuchal rigidity (neck muscles contract involuntarily, resulting in neck pain and resistance to neck flexion).
How quickly do the symptoms of infectious meningitis progress?
The symptoms may progress over hours or weeks; you need a sample of CSF (usually obtained through lumbar puncture-until someone finds a better way; be sure to have a CT before doing LP because removing CSF if there is a mass can cause herniation.
How do we treat infectious meningitis?
Antibacterial therapy.
What are some complications associated with infectious meningitis?
There's a host of them: seizures, cranial neuropathies, edema, hydrocephalus, herniation, infarcts, and last but not least, death.
What is a brain abscess and where does it occur?
It is described as an expanding intracranial mass lesion, like a brain tumor, but with a more rapid course. It occurs, of course, in the brain, specifically, intracranially. Symptoms include lethargy, headache, fever, nuchal rigidity, vomiting, seizures and focal signs.
Where does an epidural abscell occur?
These are found in the spinal canal. Symptoms include back pain, fever, headache and signs of nerve root or spinal cord compression. They are treated by surgical drainage and antibiotics.
A subdural empyema is characterized by what?
It is a collection of pus in the subdural space, usually the result of an infection of the nasal sinus or inner ear. They are usually treated by surgical drainage and antibiotics.
Tuberculous meningitis is associated with what pulmonary disorder?
Tuberculosis, in fact, it is usually seen with the resurgence of TB. Symptoms include headach, lethargy, emningeal signs over a course of weeks, on imaging one may see an inflammatory response in the basal cisterns affecting the circle of Willis and causing infarcts; coma and death if untreated. Treatment is listed as a combination of drugs but nothing specific is mentioned. Populations at risk for Tuberculous meningitis are IV drug users, Individuals who are HIV+ and populations where TB is endemic.
Neurosyphilis has seen a recent resurgence due to HIV. Neurosyphilis is caused by what organism?
Spirochetes. A primary symptom may be canker sores, secondary are diffuse skin lesions and tertiary, seen on imaging, are diffuse white matter infarcts causing dementia, bheavioral change, delusion, psychosis, upper motor neuron weakness; Tabes Dorsalis-look for Romburg sign.
The spread of Lyme disease has been blamed on what organism?
a. birds
b. fleas
c. deer ticks
d. rats
c. deer ticks
Symptoms include: an early rash; neurologic manifestations (after several weeks) meningeal signs, emotional changes, memory and concentration problems, cranial and peripheral neuropathies, arthritis, and cardiac abnormalities.
It is diagnosed by its clinical features, LP and a blood test. The disease is treated by IV ceftriaxone.
True or false:One never truly recovers from viral meningitis.
False. it is less intense, though more rapid in its progression than its bacterial brother. Recovery from Viral meningitis occurs spontaneously in 1-2 weeks.
What are the symptoms of viral meningitis?
Headache, fever, lethargy, nuchal rigidity, meningeal irritation. It is diagnosed by blood tests, LP, and EEG.
Name some causes of viral meningitis.
Herpes=psychotic symptom, focal signs, causes necrosis of temporal and frontal structures.
Postinfectious encephalitis-several days after viral infection, diffuse autoimmune demyelination of CNS.
Herpes zoster-shingles, chicken pox
Transverse myelitis-caused by viral infections of the CNS (spinal cord).
Name some HIV-Associated Disorders of the Nervous System.
Aseptic meningitis-caused at time of seroconversion and is associated with cranial neuropathies involving vacial nerve.
AIDS Dementia Complex-sometimes called ADC-most common neurologic manifestation of HIV;treat with AZT,
Progressive multifocal leukoencephalopathy (PML)-gradual demyelination of the brain, leading to death in 3-6 months. Opportunistic infections (viral, bacterial, fungal and parasitic)-herpes, varicella-zoster, cytomegalovirus (CMV), TB, neurosyphilis, cryptococcal meningitis, toxoplasmosis.
Primay central nervous system lympohoma-B cell lymphoma; second most common cause of mass lesions.
Cysticercosis is an example of what kind of infection?
Parasitic-it is associated with ingestion of the eggs of a pork tapeworm. The organism migrates through the bloodstream, forms small cysts in muscles, eyes and CNS, cuases sizures, headache, lymphocytic meningitis and hydrocephalus if the cyst obstructs.
What does cysticercosis look like on imaging, what is the course, and how is it diagnosed?
It appears as small cysts in the parenchyma with surrounding edema. The organisms eventually die leaving calcifications throughout the brain ("brain sand") and it is diagnosed through a thorough clinical history, radiologic appearance and antibody tests.
Fungal infections can involve:
a. brain parenchyma
b. cause an inflammatory response
c. cause cranial nerve deficits
d. all of the above
d. all of the above
a protein-based infectious agent; able to transmit illness from one animal to another (and apparently replicate) without DNA or RNA.
Symptoms of Prion-Related Illnesses
There is diffuse degeneration of the brain and spinal cord. Vacuoles are present that give the tissue a spongiform appearance.
Types of Prion-Related Illnesses
Creutzfeldt-Jakob; Gerstmann-Straussler-Cheinker; kuru; fatal famlial insomnia.
Creutzfeldt-Jakob Disease (CJD)has a number of debilitating symptoms. Name as many as you can...
rapidly progressive dementia, exaggerated startle response, myoclonus, visual distortion, ataxia. Other characteristics include EEG findings of a period(?) sharp wave complex. There is progressive deterioration and death within 6-12 months, the incubation period may last from 2 to 25 years and in at least one strain, there is some genetic susceptibility.
An LP or lumbar puncture may be used to determine a number of difficult diagnoses. What is accessed and what function does it perform?
The LP allows access to the subarachnoid space of the lumbar cistern (this is the place where the needle is inserted). Samples of CSF may be obtained, a measure of CSF pressure can be performed, it may be done to remove excess CSF as in the case of normal pressure hydrocephalus and is the site of intrathecal drug administration. A finding of red blood cells could indicate a subarachnoid hemorrhage or a traumatic tap due to needle puncture.
Name some disorders or diseases where LP might be used to help make a diagnosis.
Infectious processes, hemorrhage, neoplasms, meningitis and multiple sclerosis.
Burr holes are made in the skull with the use of a special saw, a bone flap is created and removed for replacement later. The dura is folded back to provide access to the brain.

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