Scenarios Flashcards
What are the main causes of a mass in the posterior fossa of an adult?
Met Met Met
What is the differential diagnosis of a posterior fossa mass in an adult?
A - Tumour 1) Metastasis 2) Haemangioblastoma (10%) - mural nodule with cyst. Look for flow voids 3) Pilocytic astrocytoma - young adults 4) Brainstem glioma 5) Choroid plexus tumour 6) Cerebellar liponeurocytoma B - Infection (Abscess) C - Vascular (cavernoma / haemorrhage / infarct)
What are the radiological features of Lhermitte-Duclos?
Tiger stripes with widening of the folia. Non-enhancing. Can be focal or diffuse.
What is the DD of multiple posterior fossa lesions?
1) Metastases 2) Abscess 3) Haemangioblastoma (think VHL!) 4) Cavernomas
What proportion of paediatric tumours are in the posterior fossa?
2/3
What is the differential diagnosis of a posterior fossa tumour in a child?
1) PNET incl Medulloblastoma 2) Pilocytic astrocytoma 3) Brainstem glioma 4) Ependymoms 5) Choroid plexus papilloma 6) ATRT 7) Mets (neuroblastoma / rhabdomyosarcoma / Wilms)
What is the most common location for a medulloblastoma?
Roof of the 4th ventricle (fastigium)
How can medulloblastomas be differentiated from ependymomas?
1) Medulloblastomas may show the ‘banana sign’ where there is a cleft of csf between the lesion and the floor of the 4th V. 2) Medulloblastomas are haemogenous 3) Calcification more common with ependymomas 4) Ependymomas grow out of the foramen of lushka
What are the molecular subtypes of medulloblastoma?
1) Wnt (10%) - usually in the cerebellar peduncle. Associated with a mutation in the b-catenin gene. Best prognosis. 2) SHH (20%) - usually in the cerebellar hemisphere. Intermediate prognosis. Associated with mutations in PTCH, SUFU, GLI1 and GLI2. 3) Group 3 (30%) - Midline with prominant enhancement. MYC amplification; GABAergic expression. 4) Group 4 (40%) - Midline with little enhancement. CDK6 and MYCN mutations. Glutamatergic expression.
What is the most common location for a pilocytic astrocytoma in a child?
Cerebellar hemisphere
Where do ependymomas arise from?
Floor of the 4th ventricle
What is the DD of a CP angle lesion?
Vestibular schwannoma Meningioma Epidermoid Metastasis Trigeminal / facial schwannoma Arachnoid cyst Neurenteric cyst Aneurysm Extension of glioma Cholesterol granuloma
What are the causes of a cystic lesion in the CP angle?
Arachnoid cyst Epidermoid cyst (restricted DWI) Dermoid cyst (high T1 and midline) Cystic schwannoma Neurenteric cyst
What is the classical presentation of a vestibular schwannoma?
Progressive unilateral hearing loss with tinnitus Vertigo is rare CN5 involvement does not occur unless >3cm - check the corneal reflex! Facial nerve involvement suggests a meningioma
Where do CP angle meningiomas arise from?
The superior anterior edge of the IAC Facial nerve palsy before hearing loss and more commonly have trigeminal neuralgia
What lesions affect the petrous apex?
Gragenigo’s syndrome Cholesterol granuloma Aneurysm SCC Glomus tumour Chondrosarcoma
What is the differential diagnosis of a foramen magnum lesion?
Meningioma Chordoma Epidermoid Chondrosarcoma Metastasis Exophytic lesion arising from the brainstem
What is the DD of white matter lesions?
1) Ischaemia (small vessel) 2) Demyelination 3) Vitamin def 4) Viral (PML/ HSV. HIV/CMV) 5) Metabolic derangements (CPM) 6) Low grade glioma
What is the DD of a lesion in the corpus callosum?
Butterfly GBM
Lymphoma
MS
Tumefactive demyelination
Lipoma
DAI
What is the DD of a pituitary tumour?
Adenoma / Carcinoma Craniopharyngioma Rathke cleft cyst Germ Cell Tumour Metastasis Aneurysm Astrocytoma Hypothalamic glioma Optic nerve sheath tumour Epidermoid cyst Chordoma Arachnoid cyst Pseudotumour i.e. physiological enlargement in puberty / pregnancy
What are the classical MR spectroscopy features of a low grade tumour?
Choline - Cr - NAA peaks form a 45 degree angle (Hunter’s angle)
What is the triad of clinical features associated with a suprasellar GCT?
DI, Panhypopituitarism and visual deficit
Lesion in the pineal and pituitary region. What is the diagnosis?
Synchronous GCT
What are the two types of hypophysitis?
Lymphocytic (late pregnancy / post partum) and granulomatous
How can hypophysitis be distinguished from a pituitary adenoma?
Hypophysitis has dilation of the pituitary stalk, symmetric pituitary enlargement, intense enhancement and loss of the posterior pituitary bright spot.
What is the difference between Schizencephaly and Porencephaly?
Schizencephaly is lined by grey matter (can be open or closed lip) whilst porencephaly is not lined by grey matter
What is the term given to when there is separation of the fornix and the roof of the 3rd ventricle?
Cavum velum interpositum
What is the difference between a cavum septum pellucidum and cavum septum vergae?
The CSP is anterior to the columns of the fornix whilst the CSV is posterior to the columns of the fornix
What is the differential diagnosis of a cavernous sinus lesion?
Meningioma Neurinoma Metastasis Pituitary tumour Lymphoma Aneuryms CCF Chordoma
What is Tolosa-Hunt syndrome?
Inflammation affected the superior orbital fissure / Cavernous sinue causing painful opthalmoplegia
What is the differential diagnosis of an intraventricular tumour?
Astrocytoma Colloid cyst Craniopharyngioma SEGA Meningioma Ependymoma / Subependymoma Craniopharyngioma Medulloblastoma (4th vent) Choroid plexus papilloma Central neurocytoma
What is the differential diagnosis of diffuse meningeal thickening / enhancement?
Intracranial hypotension Meningitis Carcinomatosis Metastasis Sarcoid / TB
What condition causes injury to the caudate and putamen?
Hypoglycaemia
What condition causes atrophy of the caudate only?
Huntingtons chorea
Describe the imaging findings.
The T2W reveals lesions in the right cavernous sinus and CPAs bilaterally.
The cavernous sinus lesion appears to be extending from Meckel’s cave and may represent a trigeminal schwannoma or meningioma.
The T1W contrast image reveals nodular enhancement of the left cisternal CN5 as well as the right cavernous sinus lesion and left VS.
The findings would be in keeping with NF2 in which schwannomas, multiple meningiomas and ependymomas are associated.
Describe the imaging findings.
The T1W contrast enhanced image reveals a large right CPA lesion extending into and widening the IAM (Trumpet sign). There is significant brainstem compression with mass effect on the right middle cerebellar peduncle and cerebellar hemisphere. The 4th venticle appears displaced and effaced but remains patent.
The hypointense non-enhancing component in centre represents an intramural cyst.
Describe the image.
The coronal T2 image centred on the right IAM shows a lesion superior to the falciform (horizontal crest), which most likely represents a Koos 1 vestibular schwannoma of the superior division of the vestibular nerve. A loop of the AICA can also be seen entering the meatus.
Describe the image.
Axial GRE sequence showing a blooming artefact within a large right CP angle lesion indicative of microhemorrhages within a vestibular schwannoma. The differential would be calcification within a meningioma.
Describe the image.
T1 and T1 contrast-enhanced images of a right CPA reveal vestibular schwannoma extending into the right IAM. There is peripheral enhancement. The central region returns high T1 signal indicating intramural cystic change due to haemorrhage.
Describe the image.
Diffusely contrast-enhancing lesion overlying the left IAM with a dural tail extending along the petrous dura. There are flow voids extending radially in a fan shape distribution representing the dural blood supply to the core. The features suggest a CP angle meningioma. The differential includes a vestibular schwannoma, dural metastasis, epidermoid cyst or inflammatory pseudotumour.
Describe the image.
Coronal T1 with contrast reveals a large contrast-enhancing lesion extending from the tentorium to the level of C1. There is invasion of the IAM, middle ear, jugular foramen and foramen magnum. These findings would be indicative of a meningioma as there appears to be a tentorial dural tail. It would be important to understand how ventral the lesion extends and its relationship to the vertebral artery,
What is the dural blood supply to the posterior fossa meninges?
Vertebral arteries
Occipital arteries
Ascending pharyngeal arteries
Note supply to the tentorium is via the meningohypophyseal trunk, posterior meningeal artery (from the Ascending pharyngeal and vertebral arteries) and the artery of Davidoff and Schecher.
Describe the image.
Coronal contrast T1 reveals a lesion in the right CPA causing mass effect on the adjacent brainstem. There is normal contrast enhancement of the contralateral choroid plexus. There does not appear to be any leptomeningeal enhancement.
Axial FLAIR reveals a substantial vasogenic edema in the right brachium pontis and deep cerebellar nuclei. The left flocculus is normal.
Where is the cochlear nucleus?
In the lateral inferior cerebellar peduncle (blue arrow). i.e. anterior border of foramen of Luschka
What hypodense lesions are found in the CPA?
Lipomas (bright on T1 and T2 and dark on fat-saturated sequences. Chemical shift artefact)
Arachnoid cysts - follows CSF no restricted diffusion
Epidermoids - follows CSF with restricted diffusion
Neuroenteric cysts - bright on T1 due to proteinaceous content and does not fat-saturate
Describe the image.
CT scan reveals a hypodense lesion at the fundus of the right IAM. The Hounsfield units appear lower than that of CSF in the 4th ventricle but not as low as air suggesting that is a lipoma. The T1 image reveals high signal intensity confirming this is a CP angle lipoma. Fat saturated images would be helpful. The differential would be an epidermoid or haemorrhage into an arachnoid cyst.
Describe the image.
CT - low-density lesion in the left CPA.
FLAIR - incomplete fluid attenuation. The surrounding region of increased FLAIR signal in the cerebellum indicates gliosis within the cerebellar hemisphere.
DWI - restricted diffusion.
These findings are suggestive of an epidermoid cyst. The differential includes neurenteric cyst (would be bright on T1 due to proteinaceous fluid content).
What are the histological features of an epidermoid?
Macro - pearly white mass with lobulated / cauliflower appearance. Filled with soft creamy/waxy material.
Micro - Cyst wall is stratified squamous epithelium with a fibrous capsule. Cyst contains keratin and cholesterol-rich fluid. No dermal derived tissue (skin / hair follicles) otherwise would be a dermoid!
Describe the image.
T1W contrast enhanced image reveals a lesion in the right CPA. This does not show contrast enhancement. The lesion has irregular borders and extends through and expands the foramen of Luschka.
The T2W image reveals high signal. I would expect a FLAIR image to show incomplete fluid suppression and a diffusion-weighted image to show restriction in keeping with an epidermoid.
What causes arachnoid cysts to form?
Congenital splitting of the arachnoid resulting in a CSF filled cavity. These follow CSF on all sequence, have no contrast enhancement and do not show restricted diffusion. The differential is an arachnoid cyst, neurenteric cyst or cystic neoplasm e.g. cystic vestibular schwannoma / cystic meningioma.
What is a Bell’s palsy?
An idiopathic facial nerve palsy thought to be due to reactivation of HSV in the geniculate ganglion.
Describe the imaging in this patient with right trigeminal neuralgia
T2 sequence of revealing a hyperintense region in the lateral pons at the exit of the trigemimal nerve. There is no vascular conflict visible. The findings would be suggestive of MS or a focal brainstem tumour as the cause of the TN. Further imaging of the brain and CSF examination would be warranted.
Describe the image in this patient with hemifacial spasm.
MRA reveals an ectatic vertebral artery with a PICA branch in contact with the root entry zone of the CN7.
Axial CISS confirms vascular conflict with the CN7/8 complex and displacement posteriorly causing kinking at the posterior margin of the porus.
What are the treatment options for hemifacial spasm?
Conservative
Medical with botox injections (needs repeating every 4 months)
Surgical with MVD of the facial nerve.
How does the patients age affect the differential diagnosis of a pituitary lesion?
Children are more likely to have craniopharyngiomas and pilocytic astrocytomas of the hypothalamus / optic pathway.
Adults are more likely to have pituitary adenomas, meningiomas and aneurysms.
What are the causes of pituitary hyperplasia?
- Physiological - puberty / pregnancy
- End organ dysfunction (primary hypothyroidism / adrenal dysfunction etc)
- Intracranial hypotension and dAVFs due to venous engorgement
What are the causes of pituitary gland infiltration?
Inflammatory (lymphocytic / granulomatous) hypophysitis
Neurosarcoidosis
Lymphoma
TB
Metastasis
What is the cause of a suprasellar mass in a child?
- Craniopharyngioma
- Pilocytic astrocytoma of the hypothalamus / optic pathway
- Germinoma (F>M)
- Histiocytosis
What is the cause of a suprasellar mass in an adult?
Pituitary macroadenoma
Meningioma
Aneurysm
Craniopharyngioma (papillary subtype)
Rathke’s cleft cyst
Metastasis
What is the 90% rule with craniopharyngiomas?
90% calcified
90% cystic
90% enhance
Describe the anatomical structures in this pituitary region
Non-contrast T1 shows normal posterior pituitary bright spot in 80%. This does not suppress with fat saturation. Contrast administration shows diffuse enhancement of the anterior and posterior pituitary, infundibulum and tuber cenereum.
The diaphragma sella forms the roof of the sella and that this point the arachnoid does not continue into the sella so this pituitary gland is not surrounded by CSF.
Describe the image.
Sagittal T1 contrast image shows a complex heterogenous sellar and suprasellar lesion with both solid and cystic components. The floor of the third ventricle is elevated and optic chiasm is displaced and not discernible. There is no synchronous lesion in the pineal region.
These features are in keeping with an adamatinomatous craniopharyngioma.
Describe the image.
Coronal T1 with contrast reveal a complex sellar and suprasellar lesion with extension laterally through the right choroidal fissure resulting in mass effect and displacement of the right basal ganglia. The hyperintense region at the lateral margin is indicative of haemorrhage. These findings in an adult are in keeping with a macroadenoma.
What is the diagnosis?
Ectopic posterior pituitary. Located at the floor of the third ventricle in the median eminence of the hypothalamus.
What are the features of hypothalamic dysfunction?
Hyperphagia>morbid obesity
Temperature dysregulation
Sleep-wake cycle disturbance
DI
Hyperproloactinaemia
Precocious puberty
Rage attacks
What is the diagnosis?
Septo-optic dysplasia.
The optic chiasm is extremely thin.
The posterior pituitary bright spot is at the median eminance in the floor of the third ventricle.
There is no infundibulum or anteiror pituitary gland visible.
Due to the absence of the septum pelludicum the fornix is very low lying.
What is the diagnosis?
Hypothalamic hamartoma (pedunculated subtype). The lesion is midway between the infundibulum and the mammillary bodies and is isointense to grey matter. Presentation is with hypothalamic dysfunction (hyperphagia, temperature dysregulation, altered sleep-wake cycles, rage attacks, DI, endocrinopathy), precocious puberty and gelastic seizures.
The differential is an ectopic posterior pituitary, craniopharyngioma, germinoma and hypothalamic pilocytic astrocytoma / opg.
What is the diagnosis?
Sessile HH.
The lesion is in the floor of the third ventricle with appearances of grey matter on both T2 and FLAIR sequences arising from the lateral wall of the inferior third ventricle. This would not enhance with contrast.#
Hypothalamic hamartomas are associated with Pallister-Hall syndrome.
What is this sellar / suprasellar lesion?
The appearances are that of a Rathke’s cleft cyst.
The CT does not reveal any calcification allowing distinction from a craniopharyngioma.
These are non-enhancing and are situated between the anterior and posterior pituitary (in the pars intermedius).
There is elevation of the optic chiasm.
What is the success of medical therapy for prolactinomas?
80-90%
What is dynamic contrast-enhanced MRI for pituitary lesions?
T1 coronal MRI taken at 5-second intervals after bolus contrast administration.
Thin coronal slices with no gap.
May reveal a filling defect with microadenomas as these enhance slower than the surrounding normal pituitary gland.
Where are prolactin and ACTH (Cushing’s) adenomas usually located?
Prolactin = peripheral
Cushings = central
What is the classical radiological appearance of a macroadenoma?
Snowman. There is elevation of the chiasm.
What is the diagnosis?
Large sella and suprasellar mass with invasion of the right cavernous sinus reaching the lateral border and circumferential encasement of the right carotid artery = Knosp grade 4.
If this is not a prolactinoma and surgery is performed then the sellar and suprasellar components can be resected but the cavernous sinus portion should be left and given SRS (20 Gy for non-functional and 25 Gy for functional).
The differential diagnosis includes craniopharyngioma, meningioma, germ cell tumour, hypothalamic pilocytic / OPG, metastasis and aneurysm.
Describe the imaging.
T1 sagittal image revealing a sellar and suprasellar lesion with erosion of the clivus and extension into the nasopharynx. There is invasion of the third ventricle which appears occluded. The lesion is heterogenous with regions of mural cystic degeneration. The posterior pituitary bright spot can be seen.
What is the diagnosis?
T1 midline sagittal section through the pituitary fossa revealing a sellar lesion expanding the sphenoid sinus extending into the sphenoid sinus. The thick skull and enlarged frontal sinuses are indicative of macroadenoma associated with acromegaly.
The differential of a macroadenoma includes apoplexy, craniopharyngioma, chordoma, meningioma and metastasis.
What is suggested by sudden onset headache, ophthalmoplegia and endocrinopathy?
Pituitary apoplexy - usually into a preexisting macroadenoma
Describe the image?
T2 coronal reveals a complex sellar and suprasellar heterogenous mass extending into the third ventricle and right cavernous sinus.
The sagittal contrast T1 image shows a fluid level anteriorly. There is patchy enhancement suggestive of necrosis in the non-enhancing components.
This is pituitary apoplexy into a macroadenoma. The differential diagnosis includes craniopharyngioma, macroadenoma, RCC, giant sellar aneurysm and germinoma.
Treatment includes steroids, urgent endocrine assessment, visual field assessment. Early surgical decompression (<7 days) is controversial.
What syndrome is pituitary apoplexy associated with?
HELLP syndrome: Haemolysis, Elevated Liver enzymes, Low Platelets
Sheehan syndrome: Peripartum infarction / haemorrhage into the anterior pituitary
What are risk fx for pituitary apoplexy?
Hypertension
Major surgery e.g. cardiac
Anticoagulation
Head trauma
Pregnancy (Sheehan’s syndrome)
What is the differential or a cerebellar lesion in an adult?
Mets Mets Mets Abscess (look at the mastoids!) Hemangioblastoma GBM Pilocytic astrocytoma / medulloblastoma (young adults) Ependymoma / subependymoma Epidermoid / dermoid Choroid plexus papilloma Cavernoma Stroke Lhermitte-Duclos (dysplastic gangliocytoma)
What is the differential or a cerebellar lesion in a child?
Medulloblastoma Ependymoma Pilocytic astrocytoma Met (Wilms / rhabdomyosarcoma / neuroblastoma) DIPG Choroid plexus papilloma
What is the differential or a CP angle lesion?
Vestibular schwannoma Meningioma Trigeminal / lower cranial nerve schwannoma Met Brainstem glioma Abscess Epidermoid Aneurysm Glomus tumour Chordoma Neurenteric cyst
How do you differentiate a vestibular schwannoma from a meningioma?
VS present with progressive unilateral SN hearing loss, facial nerve weakness is late. Loss of corneal reflex when >3 cm. Heterogenous enhancement. IAC becomes enlarged. Not calcified. Meningiomas arise from the superior edge of the IAC and cause early facial nerve weakness. Hearing loss is late. Trigeminal neuralgia is more common. Homogenous enhancement. IAC not enlarged. Calcify.
Differential of a petrous apex lesion?
Gradenigo’ syndrome Cholesterol granuloma SCC Glomus tumour Chrondrosarcoma (displaces the carotid laterally)
Differential of a foramen magnum lesion?
Meningioma Chordoma Chrondrosarcoma Met Epidermoid Pannus Exophytic brainstem tumour
What is a rotating paralysis?
Seen with FM lesions. Weakness affects the ipsi UL > ipsil LL > contra LL > contra UL
What type of nystagmus occurs with FM lesions?
Classically down beat
How do you differentiate a GBM from an abscess?
Clinical condition of the patient (fever/WCC/CRP etc) Ring enhancement is complete and thick with abscess. Strong restricted diffusion.
What is leukoencephalopathy?
Disease confined to the WM - likely demyelinating lesion (MS / ADEM).
Differential of a corpus callosum lesion?
Lymphoma, MS, ADEM, GBM, lipoma, Diffuse axonal injury
The differential of a sellar lesion?
Adult = pituitary adenoma > craniopharyhngioma , meningoma of tuberculum sella, aneurysm Child = Craniopharyngioma, germinoma, rathke’s cleft cyst > pituitary adenoma. OPG in NF1. Suprasellar arachnoid cysts Other things = Langerhans histiocytosis / lymphocytic hypophysitis *Enlarged pituitary may be physiological (pregnancy / pubertry)
How do you differentiate pituitary adenoma from lymphocytic hypophysitis?
Hypophysitis is common surrounding pregnancy. Symmetrical diffuse thickening of gland and stalk. Intense enhancement. Loss of pituitary bright spot.
What are the types of autoimmune hypophysitis?
Lymphocytic and granulomatous.
Most important clinical feature for lymphocytic type is that it occurs peri-pregnancy
Treat with steroids!
What intracranial cyst do you know?
Arachnoid cysts
Epidermoid cysts
Porencephalic cysts
Schizencephaly
Neuroenteric cysts
Pineal cyst
Colloid cysts
Haemoangioblastoma
Cystic meningiomas
Cystic schwannomas
Infective cysts (neurocysticerosis secondary to taemia solium and hydatid cyst secondary to echinococcus)
How do you differentiate cavum septum, cavum vergae and cavum velum interpositum?
Cavum septum is anterior to foramen of monroe between the leaflets of septum pellucidum.
Cavum vergae is posterior to foramen of monroe. Associated with Apert’s syndrome!
Cavum velum interpositum extends below the splenium and above the roof of the 3rd ventricle / internal cerebral veins. It is due to separation of the crura of the fornix and the thalamus.
What is the differential of an orbital lesion?
Pseudotumour (most common intraconal lesion)
Meningioma
OPG
Optic nerve schwannoma
Cavernoma
CCF/AVM
Melanoma
Retinoblastoma
Lymphoma
Grave’s disease
Fibrous dysplasia
Dermoid (in a child)
What is the differential of a cavernous sinus lesion?
Meningioma
Schwannoma
Pituitary adenoma
Chordoma
Metastasis
Lymphoma
Mucocele
Tolosa Hunt syndrome
Cavernous sinus aneurysm / fistula / thrombosis
What are the causes of leukoencephalopathy?
Demyelination (MS/ADEM)
Infections (PML/HSV/CMV)
Hyponatraemia
Metachromic leukodystrophy
Toxins (Carbon monoxide/ cyanide etc)
Vitamin def (B12)
Low grade glioma
How do you categorise orbital tumours?
Ocular / Optic nerve / Intraconal / Extraconal
What is the most common orbital lesion?
Orbital cavernous haemangioma (cavernoma)
Displaces the optic nerve and rectus muscles (intraconal)
Well defined
Bright on T2
Progressive filling enhancement pattern
Treatment is conservative unless they grow or are symptomatic and then surgical removal is curative
Differential is a schwannoma / meningioma / melanoma / lymphoma
What is the main difference between a capillary haemangioma and a lymphangioma?
Both causes infantile proptosis. Capillary haemangiomas regress spontaneously whilst lymphangiomas do not! Lymphangiomas get worse with URTIs. MRI of a lymphangioma is shown.
What is this?
Capillary haemangioma
What is this?
Dilated opthalmic artery (white arrow heads) seen filling into dural AVF (black arrow). Dilated venous varices (white arrows) seen in later phase.
What is this condition?
Wyburn-Mason syndrome.
Telangiectasia on the face. AV extending from the orbit along the optic pathway to the midbrain with large varix draining into the superior petrosal sinus.
What is this?
A CCF with an arterialised superior ophthalmic vein
What is an orbital pseudotumour?
The most common orbital lesion in adults.
Idiopathic inflammatory lesion of the orbit that involves the extraocular muscles (most commonly the lateral rectus)
Rule out Grave’s disease!
What is leontiasis ossea?
Fibrous dysplasia of the skull and face which makes the patient look like a lion!
Which tumours can have a dural tail?
Meningioma
Pleomorphic xanthroastrocytoma (see picture)
What is the cause of bilateral high T1 signal in the globus pallidus?
Manganese toxicity
What are the causes of atlantoaxial subluxation with increased ADI?
Rheumatoid arthritis (erosion of the entry point of the transverse ligament) Trauma Congenital laxity (Downs / NF) Retropharyngeal infection (Grisel syndrome) Chronic steroid use
What are the causes of atlantoaxial subluxation with normal ADI?
Odontoid fracture Os odontoideum (orthotopic type) Erosion of the odontoid due to Rheumatoid arthritis Neoplastic erosion of the odontoid Morquio syndrome - hypoplasia of the odontoid Transoral / endonasal odontoidectomy
What primary bone tumours affect C2?
Chondroma
Chondrosarcoma
Osteoblastoma
Osteoid osteoma
Osteosarcoma
Chordoma
Giant cell tumour
Aneurysmal bone cyst (see picture)
What causes pulsatile exopthalmos?
CCF NF-1 with sphenoid wing dysplasia / orbital roof defect causing transmitted pulsations Vascular tumours
What causes pulsatile exopthalmos?
CCF NF-1 with sphenoid wing dysplasia / orbital roof defect causing transmitted pulsations Vascular tumours
Where does the piriformis muscle attach?
From the VB of S2-3, through the greater sciatic notch to the greater trochanter
How do you differentiate deep, superficial and common peroneal nerve injuries?
Deep peroneal nerve injury causes a pure motor foot drop with loss of ankle eversion.
Superficial peroneal nerve injury causes a numb lateral leg but no foot drop. There is a weakness of eversion due to peroneus longus.
Common peroneal nerve injury causes both weakness and numbness.
How do you localise a sciatic nerve lesion?
Root lesion - paraspinal muscle weakness
Lumbar plexus - weakness of gluteus medius (hip abduction) and maximus (hip extension) but sparing of paraspinal muscles
Sciatic nerve (prox to common peroneal nerve branch) - biceps femoris (flexion of the knee) and gastrocnemius (plantar flexion) are weak
Tibial nerve (weakness of tibialis posterior so cannot invert the foot).
Deep peroneal nerve causes foot drop through weakness of tibialis anterior
Supfl peroneal nerve (weakness of ankle eversion but no foot drop)
What is Bell’s cruciate paralysis?
Where a foramen magnum lesion causes upper limb but not lower limb weakness due to compression of the medulla at the site of the UL decussation but sparing the more laterally located LL fibres that decussate lower.
Label the structures:
1 = S2 VB
2 = SI joint (synovial portion)
3 = SI joint (non-synovial portion)
4 = Sacral ala
5 = Iliac bone
6 = S2 root
7 = S3 root
8 = Multifidus
9 = Glut. maximus
10 = Glut. medius
Label the structures on the CT myelogram:
- Odontoid process
- C1 lateral mass
- Lateral neural arch
- Posterior neural arch
- CSF
- Spinal cord
- Anterior midline tubercle
- Foramen transversarium
- Dorsal rootlet
- Rectus capitus posterior major
- Semispinalis capitus
- Tubercle of the transverse ligament
What are the muscles of the suboccipital triangle?
Trapezius is more superficial. SCM being lateral. Both attach to the superior nuchal line
Then Semispinalis (medial) and splenius capitus (lateral)
Rectus capitus post. major - C2 spinous process to the inferior nuchal line
Inferior oblique - C2 spinous process to C1 lateral tubercle
Superior oblique - C1 lateral tubercle to inferior nuchal line
(The rectus capitus posterior minor attaches from the C1 lamina to the inferior nuchal line)
What are the muscle attachment at the back of the skull?
Label the structures:
- C4 VB
- Spinal cord
- C5 sup articular process
- C4 inferior articular process
- Lamina
- Spinous process
- Vertebral artery
- Facet joint
- C5 DRG
- Dorsal rootlet
- Ventral rootlet
- Longus coli
- Multifidus
- Semispinalis capitus
- Splenius captius
- IJV
17 ICA
What nerves supply the scalp and face?
- Supratrochlear (from V1)
- Supraorbital (from V1)
- Infratrochlear (from V1)
- External nasal (from V1)
- Infraorbital nerve (from V2)
- Lacrimal (from V1)
- Zygomaticotemporal (from V2)
- Zygomaticofacial (from V2)
- Auriculotemporal (from V3)
- Buccal (from V3)
- Mental (from V3)
- Greater auricular (C2/3)
- Transverse cervical (C4)
- Supraclavicular (C4)
- Greater occipital (C2)
- Lesser occipital (C2)
Where is the hypoglossal nerve during high ACDF approach?
Beneath the posterior digastric running between the ICA and IJV. Runs deep to mylohyoid on the surface of hyoglossus
Which windows are tcds performed through?
Temporal, orbital, suboccipital and submandibular
How do you read a Vernier scale?
Align the 0 on the Vernier scale with the rule scan to get the mm distance. Then whichever of the Venier lines that lines up with the rule scale lines tells you the next decimal value.
In the picture, the answer is 2.1 mm as the 0 on the vernier is at 2 on the rule scale and the 1 on the vernier is in line with the rule scale.
What methods are used to identify the motor cortex?
Phase reversal (performed asleep) - a strip is placed traversing the central sulcus covering precentral and postcentral cortices. SSEPs are undertake with peripheral stimulation. Phase reversal of N20 to become P20 indicates the location of the central sulcus.
Direct cortical / subcortical stimulation (awake surgery)
How do you place a patient in the park bench position?
Position the patient at the top of the table so the arm can extend down over the top.
Place a roll under the chest wall (not pushed into the axilla, as this may damage the brachial plexus).
Upper arm / shoulder are taped downward and forwards to open the working space.
Head placed in mayfield clamp looking 30 degrees to the floor.
Elevate the head 15 degrees.
Round bolster placed at the ASIS and flat bolster on the back.
Pillow in between the knees
How do you perform a telovelar approach?
Suboccipital craniotomy and U-shaped dural opening.
The uvula is separated from the tonsils bilaterally.
The tonsils are retracted superiorly and laterally.
The PICA is visualised and protected.
The tela choroidae and inferior medullary velum are opened as the uvula is retracted.
The floor is protected by inserting a pattie.
Describe the anatomical location of structures following a pterional approach with proximal splitting of the sylvian fissure.
Optic nerve
Carotid
Anterior choroidal
PCom
ACom complex
CN3
Carotid-oculomotor approach to basilar tip
What are the approaches to the third ventricle?
Transcortical (middle frontal gyrus for anterior 1/3 ventricle) - requires dilated ventricles
Transcallosal - anterior and posterior
Subfrontal - trans lamina terminalis through subfrontal or pterional approaches and transphenoidal for suprasellar lesions extending into third ventricle
Supracerebellar infratentorial
Suboccipital transtentorial
Describe the anatomy of the ventricles from an interhemispheric transcallosal approach
Orientation by identifying the thalamostriate vein and following it anteriorly to the foramen of Monroe.
How can the window through the foramen of Monroe be expanded?
Transchoroidal (medial to the choroid plexus through the tenia fornices)
Or
Interforniceal (between the left and right fornices)
Describe how you would perform an interhemispheric transcallosal approach for a colloid cyst
In an appropriately consented and anaesthetised patient.
I would apply the Mayfield clamp and position then supine with slight head elevation (10-15 deg). Registration of neuronavigation.
Linear bicoronal incision (or box flap) at the level of the coronal suture
6 cm AP (2/3 anterior to coronal suture and 1/3 behind) x 4 cm medial-lateral craniotomy straddling the midline to give control over the SSS. Position is planned to avoid sacrificing large cortical veins.
Dura flapped over the SSS
Interhemipheric dissection following the falx
Once the falx ends you see the cingulate gyri
Dissect between the cingulate gyri to visualised the pericallosal arteries
Dissection between the pericallosals through the corpus callosum from within 2cm of the genu ensuring not to enter a cavum septum pellucidum.
How do you perform a ventriculostomy following a pterional craniotomy?
Through Paine’s point: 2.5cm above and behind the sylvian fissure. Passed directly parallel to the floor of the anterior fossa.
This is used when there is significant brain swelling to allow CSF egress.
**RISK of hitting the caudate and damaging Broca’s area on the left. In which case modify the entry to be more anterior.
What are the side effects of VIM stimulation?
Paraesthesia (too posterior - stimulation of lemniscal fibres entering the ventralis caudalis nucleus)
Dysequilibrium (due to ZI stim)
Dysarthria (too medial - stimulation of the medial Vim) or too lateral if also associated with muscle contractions - stimulation of the internal capsule)
Ataxia (too ventral and medial - stimulation fo the brachium conjunctivum)
High voltages needed for tremor suppression (too anterior due to stimulation of the ventralis oralis posterior)
Phosphenes (too deep - optic tract stimulation)
What side effects are expected with the following electrode locations for Vim stimulation?
a - electrode is too anterior and within the VOP - requires high voltages to induce tremor suppression
b - electrode is too short within the Vim - will likely not to result in any tremor suppression.
c - electrode too posteroir and within the ventralis caudalis nucleus - will likely results in paraesthesias due to leminiscal fibre stimulation
What side effects are expected with the following electrode locations for Vim stimulation?
a - medial location within the Vim. Likely to result in dyarthria.
b - deep location stimulating the ZI and brachium conjunctivum. Likely to cause ataxia.
c - lateral location so within the internal capsule. Likely to cause dysarthria and facial pulling movements/dystonia.
Label the adjacent structures to the STN (axial and coronal images shown)
Superior = ventralis oralis anterior / ZI (stim results in tremor suppression)
Inferior = Substantia nigra (stim results in akinesia)
Medial and deep = midbrain / CN3 nuclus (double vision and gaze deviation)
Anterior or Lateral = internal capsule (dysarthria and muscle contraction)
Posterior = (perspiration and mydriasis)
What are the side effects of incorrectly placed DBS electrodes?
Based on the target:
STN / VIM / GPi
