28- neuro Explains Flashcards
What is an extradural hematoma?
Bleeding into the space between the dura mater and the skull, often resulting from acceleration-deceleration trauma or a blow to the side of the head
Where do the majority of extradural hematomas occur?
In the temporal region, where skull fractures cause a rupture of the middle meningeal artery
What are the features of an extradural hematoma?
Raised intracranial pressure, and some patients may exhibit a lucid interval
What is a subdural hematoma?
Bleeding into the outermost meningeal layer, most commonly around the frontal and parietal lobes
What are the risk factors for subdural hematomas?
Old age and alcoholism
How does the onset of symptoms in a subdural hematoma differ from an extradural hematoma?
Symptoms in a subdural hematoma have a slower onset compared to an extradural hematoma
What is a subarachnoid hemorrhage?
Bleeding that usually occurs spontaneously from a ruptured cerebral aneurysm, but can also be seen in association with other traumatic brain injuries
How does diffuse axonal injury occur?
As a result of mechanical shearing during deceleration, causing disruption and tearing of axons
What are the two types of primary brain injury?
Focal (contusion/haematoma) and diffuse (diffuse axonal injury)
What are the different types of intra-cranial hematomas?
Extradural, subdural, and intracerebral
What happens to cerebral autoregulatory processes following trauma?
They are disrupted, making the brain more susceptible to blood flow changes and hypoxia
Where can contusions occur in relation to the impact site?
Adjacent to the impact site (coup) or on the opposite side (contre-coup)
What is secondary brain injury?
It occurs when cerebral edema, ischemia, infection, tonsillar or tentorial herniation worsens the original injury
What may be required for diffuse cerebral edema?
Decompressive craniotomy
What is the Cushings reflex?
Hypertension and bradycardia, often occurring late and usually a pre-terminal event
What management options are available for life-threatening rising intracranial pressure?
Use of IV mannitol/frusemide while theater is prepared or transfer is arranged
When are exploratory burr holes used in modern practice?
When scanning is unavailable and to facilitate creation of a formal craniotomy flap
What is the management for open depressed skull fractures?
Formal surgical reduction and debridement
When is ICP monitoring mandatory?
In patients with a GCS of 3-8 and an abnormal CT scan
How are closed depressed skull fractures managed?
They may be managed non-operatively if there is minimal displacement
What is the most likely cause of hyponatremia in this context?
Syndrome of inappropriate ADH secretion
When is ICP monitoring appropriate?
In patients with a Glasgow Coma Scale (GCS) of 3-8 and a normal CT scan
What is the minimum cerebral perfusion pressure required in adults?
70 mmHg
What is the minimum cerebral perfusion pressure required in children?
Between 40 and 70 mmHg
What does unilaterally dilated pupil with sluggish or fixed light response indicate?
3rd nerve compression secondary to tentorial herniation
What does bilaterally dilated pupil with sluggish or fixed light response indicate?
Poor CNS perfusion
What does bilateral 3rd nerve palsy indicate?
Bilateral dilation of the pupils
What does unilaterally dilated or equal pupils with cross reactive (Marcus-Gunn) response indicate?
Optic nerve injury
What does bilaterally constricted pupils indicate?
It may be difficult to assess, but possible causes include opiates, pontine lesions, and metabolic encephalopathy
What does unilaterally constricted pupil with preserved sympathetic pathway response indicate?
Sympathetic pathway disruption
What percentage of subarachnoid hemorrhage cases have normal angiography?
Approximately 10%
What imaging is recommended for investigation?
CT scan for all cases; lumbar puncture if CT is normal
What is the most common cause of subarachnoid hemorrhage?
Intracranial aneurysm (85% of cases)
What is the typical presentation of subarachnoid hemorrhage?
> 95% of cases have a thunderclap headache; >15% may have coma
What is the purpose of a CT angiogram in subarachnoid hemorrhage?
To look for aneurysms
What is the goal of management for subarachnoid hemorrhage?
Supportive treatment, optimizing blood pressure, ventilation if needed
What medication is used to reduce cerebral vasospasm and improve outcomes?
Nimodipine
When are untreated patients most likely to experience rebleeding?
Within the first 2 weeks
What treatment options are available for aneurysms?
Craniotomy and clipping or endovascular coiling
Which treatment option, coiling or surgery, has better outcomes according to available data?
Coiling
What is the recommended timeframe for assessing patients with head injuries in the emergency department?
Within 15 minutes of arrival
What are the three components of the GCS that should be documented in head injury patients?
Eye opening, verbal response, motor response
When should the airway be considered for stabilization in head injury patients?
If GCS is less than or equal to 8
When is full spine immobilization indicated in head injury patients?
If GCS is less than 15, neck pain/tenderness, paraesthesia extremities, focal neurological deficit, or suspected c-spine injury
What imaging modality is preferred for suspected c-spine injury?
CT c-spine
When is an immediate CT head scan recommended (within 1 hour)?
If GCS is less than 13 on admission, GCS is less than 15 two hours after admission, suspected open or depressed skull fracture, suspected skull base fracture, focal neurology, vomiting > 1 episode, post-traumatic seizure, coagulopathy (or receiving anticoagulant)
When should a neurosurgeon be contacted in head injury cases?
If there is persistent GCS less than or equal to 8, unexplained confusion lasting >4 hours, reduced GCS after admission, progressive neurological signs, incomplete recovery post-seizure, penetrating injury, or cerebrospinal fluid leak
How frequently should GCS be monitored in head injury patients?
Every 1/2 hour until GCS reaches 15
What are the two most common types of CNS tumors?
Glioma and metastatic disease (60%)
What is the second most common type of CNS tumor?
Meningioma (20%)
What percentage of CNS tumors are pituitary lesions?
10%
What are the common types of CNS tumors in pediatric practice?
Medulloblastomas (neuroectodermal tumors) and astrocytomas
Which areas of the brain may have tumors that reach considerable size before becoming symptomatic?
Right temporal and frontal lobes
What imaging technique provides the best resolution for diagnosing CNS tumors?
MRI scanning
Which areas of the brain typically produce early symptoms when tumors are present?
Speech and visual areas
Which type of tumor can usually be cured with surgery?
Meningiomas
What is the usual treatment approach for CNS tumors?
Surgery, even if complete resection is not possible, to address conditions like rising intracranial pressure and prolong survival and quality of life
What does a left homonymous hemianopia indicate?
Visual field defect to the left
Why is complete resection often not possible for gliomas?
Gliomas have a marked propensity to invade normal brain tissue
What is the difference between incongruous and congruous defects in visual field defects?
Incongruous defects suggest a lesion of the optic tract, while congruous defects suggest a lesion of the optic radiation or occipital cortex
Which structure is likely to be affected in a left homonymous hemianopia?
Right optic tract
What are homonymous quadrantanopias and what mnemonic can be used to remember them?
Quadrant visual field defects; PITS (Parietal-Inferior, Temporal-Superior)
What does the term “macula sparing” indicate in visual field defects?
Lesion of the occipital cortex while sparing the central vision (macula)
What are the likely locations of lesions causing homonymous quadrantanopias?
Superior quadrant defect suggests a lesion of the temporal lobe, while inferior quadrant defect suggests a lesion of the parietal lobe (PITS mnemonic)
What does a bitemporal hemianopia indicate?
Visual field defect involving both temporal visual fields
What is the likely location of a lesion causing an upper quadrant defect compared to a lower quadrant defect in bitemporal hemianopia?
Upper quadrant defect suggests inferior chiasmal compression, commonly due to a pituitary tumor, while lower quadrant defect suggests superior chiasmal compression, commonly due to a craniopharyngioma
What is an extradural haematoma?
Bleeding between the dura mater and the skull
Where do the majority of extradural haematomas occur?
Temporal region
What is the most common cause of extradural haematomas?
Acceleration-deceleration trauma or a blow to the side of the head
What is a potential feature of extradural haematomas?
Raised intracranial pressure; some patients may exhibit a lucid interval
What is a subdural haematoma?
Bleeding into the outermost meningeal layer
Where do subdural haematomas commonly occur?
Around the frontal and parietal lobes
What are the risk factors for subdural haematomas?
Old age and alcoholism
How do the symptoms of subdural haematomas compare to extradural haematomas?
Slower onset of symptoms
What is an intracerebral haematoma?
A hyperdense lesion in the brain
How do intracerebral haematomas typically form?
Areas of traumatic contusion fuse to become a haematoma
What should be considered when large haematomas or those causing mass effect are present?
Evacuation of the haematoma
What is a subarachnoid haemorrhage?
Bleeding that occurs spontaneously, often from a ruptured cerebral aneurysm
When does intraventricular haemorrhage commonly occur in adults?
In association with severe head injuries
What is an intraventricular haemorrhage?
Haemorrhage that occurs in the ventricular system of the brain
When do the majority of intraventricular haemorrhages occur in neonates?
First 72 hours after birth
What is a potential cause of neonatal intraventricular haemorrhages?
Birth trauma combined with cellular hypoxia and the delicate neonatal CNS
What is another name for depressed skull fractures?
Signature fractures
What causes depressed skull fractures?
Focal impact of a moving object on the cranial vault
What can high-velocity objects do in depressed skull fractures?
Not only disrupt bone, but also drive fracture fragments into the brain
What type of defect may blunt objects moving at low velocity produce in the skull?
A defect of similar dimensions to the object, known as a signature
What parts of the skull can be affected by depressed skull fractures?
The outer table alone or both the outer and inner tables
When may surgery be required for depressed skull fractures?
In cases of open fractures or fractures associated with intracranial hematomas
How can uncomplicated fractures without significant cosmetic deformities be managed?
Conservatively, without surgery
What is the initial imaging modality of choice for depressed skull fractures?
CT scanning
What is the risk of haematoma requiring removal in adults with concussion and no skull fracture who are conscious and oriented?
1 in 6,000
What is the risk of haematoma requiring removal in adults with concussion and no skull fracture who are not oriented?
1 in 120
What is the risk of haematoma requiring removal in adults with a skull fracture who are conscious and oriented?
1 in 32
What is the risk of haematoma requiring removal in adults with a skull fracture who are not oriented?
1 in 4
What is Von Hippel-Lindau (VHL) syndrome?
An autosomal dominant condition predisposing to neoplasia
Where is the abnormality in VHL syndrome located?
On the short arm of chromosome 3
What are the features associated with VHL syndrome?
Cerebellar haemangiomas, retinal haemangiomas with vitreous haemorrhage, renal cysts (premalignant), phaeochromocytoma, extra-renal cysts (epididymal, pancreatic, hepatic), and endolymphatic sac tumours
What is the primary intracerebral haemorrhage (PICH) characterized by?
Headache, vomiting, and loss of consciousness
Which arteries are involved in total anterior circulation infarcts (TACI)?
Middle and anterior cerebral arteries
What are the common symptoms of TACI?
Hemiparesis/hemisensory loss, homonymous hemianopia, and higher cognitive dysfunction (e.g., dysphasia)
Which arteries are involved in partial anterior circulation infarcts (PACI)?
Smaller arteries of the anterior circulation, such as the upper or lower division of the middle cerebral artery
What are the common symptoms of PACI?
Higher cognitive dysfunction or a combination of two of the three TACI features
Which areas are affected in lacunar infarcts (LACI)?
Perforating arteries around the internal capsule, thalamus, and basal ganglia
Which arteries are involved in posterior circulation infarcts (POCI)?
Vertebrobasilar arteries
What are the common symptoms of LACI?
Isolated hemiparesis, hemisensory loss, or hemiparesis with limb ataxia
What are the common symptoms of POCI?
Features of brainstem damage, such as ataxia, disorders of gaze and vision, and cranial nerve lesions
What is another name for lateral medullary syndrome?
Wallenberg’s syndrome
What are the symptoms of lateral medullary syndrome (Wallenberg’s syndrome)?
Ipsilateral: ataxia, nystagmus, dysphagia, facial numbness, cranial nerve palsy; Contralateral: limb sensory loss
What are the common symptoms of a stroke involving the anterior cerebral artery?
Contralateral hemiparesis and sensory loss, with lower extremity involvement greater than upper extremity. Disconnection syndrome may also occur.
What are the common symptoms of a stroke involving the posterior cerebral artery?
Contralateral hemianopia with macular sparing. Disconnection syndrome may also occur.
What is Weber’s syndrome characterized by?
Ipsilateral III palsy and contralateral weakness
What are the common symptoms of a stroke involving the middle cerebral artery?
Contralateral hemiparesis and sensory loss, with upper extremity involvement greater than lower extremity. Contralateral hemianopia, aphasia (Wernicke’s), and gaze abnormalities may also be present.
What are the common symptoms of a lacunar stroke?
Presentation with either isolated hemiparesis, hemisensory loss, or hemiparesis with limb ataxia.
What are the common symptoms of a stroke involving the lateral medulla (posterior inferior cerebellar artery)?
Ipsilateral symptoms include ataxia, nystagmus, dysphagia, facial numbness, and cranial nerve palsy (e.g., Horner’s syndrome). Contralateral symptoms include limb sensory loss.
What are the common symptoms of a pontine stroke?
VI nerve involvement leads to horizontal gaze palsy. VII nerve involvement leads to contralateral hemiparesis.
What are the features of a third nerve palsy?
The eye is deviated ‘down and out’, ptosis (drooping of the eyelid), and the pupil may be dilated (sometimes called a ‘surgical’ third nerve palsy)
What are some common causes of third nerve palsy?
Diabetes mellitus, vasculitis (e.g., temporal arteritis, SLE), uncal herniation through the tentorium (false localizing sign due to raised ICP), posterior communicating artery aneurysm (pupil dilated), cavernous sinus thrombosis
What is Weber’s syndrome?
It refers to an ipsilateral third nerve palsy with contralateral hemiplegia, caused by midbrain strokes
What are some other possible causes of third nerve palsy?
Amyloid, multiple sclerosis
Where are the cavernous sinuses located?
On the body of the sphenoid bone, running from the superior orbital fissure to the petrous temporal bone
What are the medial relations of the cavernous sinuses?
Pituitary fossa and sphenoid sinus
What are the lateral relations of the cavernous sinuses?
Temporal lobe
What are the components of the lateral wall of the cavernous sinuses from top to bottom?
Oculomotor nerve, trochlear nerve, ophthalmic nerve, and maxillary nerve
What are the contents of the cavernous sinuses from medial to lateral?
Internal carotid artery (and sympathetic plexus) and abducens nerve
What is the blood supply to the cavernous sinuses?
Ophthalmic vein, superficial cortical veins, and basilar plexus of veins posteriorly
What is the Cushing reflex?
The Cushing reflex is a physiological response that occurs when intra cranial pressure (ICP) exceeds mean arterial pressure (MAP), leading to compression of cerebral arterioles and resulting in cerebral ischemia.
Where do the cavernous sinuses drain into?
The internal jugular vein via the superior and inferior petrosal sinuses
What happens during the initial stage of the Cushing reflex?
Increases in ICP activate the sympathetic nervous system, causing a stepwise increase in peripheral vascular resistance and hypertension. Cardiac output also increases.
What triggers the second stage of the Cushing reflex?
The haemodynamic changes detected by aortic arch baroreceptors trigger the activation of the parasympathetic nervous system.
What are the parasympathetic effects in the second stage of the Cushing reflex?
The parasympathetic effects include a decrease in peripheral vascular resistance and a decrease in cardiac output.
Why is the Cushing reflex considered a serious development?
The Cushing reflex indicates imminent coning (herniation of the brainstem) or other terminal events if not resolved quickly. It serves as a warning sign of severe neurological compromise.
