What is the uncommon diagnosis in this case? It’s a difficult one!

Case: A 42-year-old male presents with a nine-month history of burning pain and numbness in his right calf which extends to the lateral aspects of the plantar surface of his foot. He has a full range of movement and normal power within his right leg and foot. There is no muscle atrophy and reflexes are normal. He has no history of trauma. What is the diagnosis?

Axial PD Fat Suppression

Axial PD Fat Suppression

Axial PD Fat Suppression

Axial PD Fat Suppression

Axial PD Fat Suppression

Coronal T2 Fat Suppression

Coronal T2 Fat Suppression

Coronal T2 Fat Suppression

 

Findings: The images demonstrate a multilobulated ganglion arising from the proximal tibiofibular joint (images D, F-G, red arrows); which extends along the articular branches of the tibial nerve to the popliteal fossa (images D-E, H, blue arrows). Extrusion of the cyst within the tibial nerve sheath from the level of the knee joint proximally over a length of four centimeters (images B-C, H, green arrows); with displacement of nerve fibers, representing the signet ring sign (image C). Perineural edema extends proximally within the tibial nerve to the sciatic bifurcation (image A).

Diagnosis: Intraneural ganglion of the tibial nerve.

Differential: Cystic peripheral nerve sheath tumor, cystic nerve degeneration from prior trauma, extraneural ganglion, adventitial cyst of popliteal artery, unusual dissecting “Baker’s cyst.”

Discussion: Intraneural ganglion cysts involving the peripheral nerves are an uncommon but recognized cause of neuropathy that can present with pain, paresthesia or muscle weakness. At the knee, the peroneal nerve is the most commonly involved, with tibial nerve involvement being extremely uncommon. The peroneal nerve may undergo primary intrinsic internal cystic degeneration after trauma especially after being impacted by a car bumper. Cystic degeneration may occur within a matter of weeks.

This case demonstrates the previously-described MRI “signet ring sign,” associated with intraneural ganglia, which represents the intraneural cyst positioned eccentrically within the epineurium of the nerve, with displacement of nerve fascicles. The communication with the proximal tibiofibular joint is well appreciated on MRI, representing the “tail sign” (red and pink arrows).

A ganglion is actually a “pseudocyst” and not a true epithelial-lined cyst. It arises from degeneration of tendon sheath or capsule with a slow leak or ooze that is marginated by fibrous tissue.

Treatment of symptomatic intraneural ganglion involves percutaneous decompression or surgical excision to reduce nerve compression and secondary muscle denervation.

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Editor’s Note: This case was submitted by Dr. Tiffany So, one of our scholarship winners for our December 2017 Melbourne course. Congratulations to Dr. So!

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Why is this woman having left-sided weakness post Chiari decompression?

This 30-year-old female presents with left-sided weakness post Chiari decompression.

Q1 – What is the most likely diagnosis?

(a) Inadequate decompression
(b) Hydrocephalus with slit ventricles
(c) Pseudomeningocele
(d) Cerebellar ptosis
(e) Dandy-Walker continuum

Try to answer the question by looking at the first five images. Then, have a look at the latter five (images 6 through 10) duplicate images with arrows added for key findings.

Sagittal T1 FLAIR

Sagittal T1 FLAIR

Sagittal T1 FLAIR

Axial T1

Axial T1

Sagittal T1 FLAIR

Sagittal T1 FLAIR

Sagittal T1 FLAIR

Axial T1

Axial T1

 

A1 – (d) Cerebellar ptosis

When evaluating causes of failure of posterior fossa decompression in Chiari, it is important to systematically check that each of the following are NOT potential causes:

  • Insufficient posterior fossa decompression
  • Overvigorous decompression
  • Unrecognized hydrocephalus
  • Pseudomeningocele formation

Chiari decompression may be indicated if a syrinx is present and in situations where neurologic findings are present or in a sterotyped clinical presentation of tussive occipital or suboccipital headaches with syrinx. The goal of surgery is decompression of the cerebellar tonsils and opening of the CSF pathways at the skull base.

Decompression requires suboccipital craniectomy and often C1 laminectomy and may also include duraplasty sufficient to unblock the CSF pathways at the skull base. Overvigorous decompression above the equator of the cerebellum may result in downward migration of the cerebellum (ptosis) which may reproduce the obstruction at the skull base. This may result in recurrent symptoms and persistence, or re-expansion of a collapsed syrinx. This is a common but poorly appreciated cause of failure of Chiari surgery.

The failure to recognize that tonsillar displacement is secondary to increased intracranial pressure or an intracranial mass, and not a true Chiari, may also result in failed surgery. This is a serious error.

Pseudomeningocele occurs most commonly when duraplasty is performed but the repair breaks down or is not water tight.

Remember that any suspected Chiari malformation seen on a cervical spine MR should always prompt an examination of the brain for other causes of tonsillar displacement such as increased intracranial pressure or decreased intrathecal pressure (intracranial hypotension), the latter of which may cause tonsillar sagging.

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Reference:

1. Holly LT, Batzdorf U. JNS 2001 Jan: 94, 21-26.

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Can you find the cause of this 29-year-old’s headaches?

This 29-year-old female presents with headache. Look at the first four images and try to determine the answer before looking at the latter four duplicate images with arrows.

Q1 – What is the most likely diagnosis?

(a) Alobar holoprosencephaly
(b) Dandy Walker variant
(c) Septo-optic dysplasia
(d) Kallman syndrome

Coronal T1

Sagittal T1

Coronal T1

Coronal T1

Coronal T1

Sagittal T1

Coronal T1

Coronal T1

 

A1 – (c) Septo-optic dysplasia

Q2 (Advanced) – MRI in septo-optic dysplasia may be associated with any of the following, except:

(a) Absence of midline cleavage involving the falx cerebri
(b) Hypoplasia of the optic apparatus
(c) CMV infection
(d) Ectopic neurohypophysis
(e) Schizencephaly

A2 – (a) Absence of midline cleavage involving the falx cerebri

Septo-optic dysplasia (SOD) is characterized by optic nerve hypoplasia and absence of the septum pellucidum. Unlike alobar holoprosencephaly, midline cleavage of the falx and thalami is preserved though it may be considered on the low end of the holoprosencephaly spectrum. CMV infection has been described as a risk factor for SOD, as have maternal diabetes and exposure to quinidine antiepileptics. SOD is associated with schizencephaly (50 percent) as well as aqueductal stenosis, rhombencephalosynapsis, Chiari II and ectopic neurohypophysis.

Absence of the olfactory bulbs can also occur as a feature which may be shared with Kallmann’s syndrome. However, without a history of hypogonadism with anosmia, that diagnosis is unlikely.

Dandy-Walker (DW) variant is a continuum of posterior fossa abnormalities including at least partial inferior vermian hypoplasia. In it’s more classic forms, DW may include enlargement of the posterior fossa, cephalad rotation of the vermian remnant, loss of the fastigial point, torcular-lambdoid inversion and cystic dilation of the fourth ventricle with obstructive hydrocephalus.

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For more case review, check out MRI Online.

Reference:

1. Barkovich AJ et. al. Septooptic Dysplasia: MR Imaging. Radiology 1989: 171 (1): 189-192.

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‘Twas the night before Christmas

This holiday season, I am grateful for the support you have given me. Sharing my love and passion for radiology with you every day is a great gift and has been the highlight of 2017. Thank you for reading every day.

In return, my Christmas gift to you is a short case. Happy Holidays everyone!

‘Twas the night before Christmas, when all through the hall, not an intern was stirring, exhausted from call. The front desk was eating the candy and tootsies, but right down the corridor lay some very sick footsies.

Q – What is wrong with the footsies?

A – Hyperintense edema on the water weighted image on the left detects ill-defined marrow swelling only with minimal distal focality. It is the “bone scan-like” sensitive sequence, lacking in specificity, but strong in detection or sensitivity.

However, when it comes to osteomyelitis, T1 is the key. If the T1 is normal, there is NO invasive osteomyelitis. In this example, the tuft of digit one has a “bite” taken out of it on T1 or the fat weighted image (red circle) along the toe’s medial cortical edge.

This is the “bone erasure sign” we have described for invasive osteomyelitis.

“So Santa descended with a PIC line and drugs, wearing his cherry red holiday scrubs. He looked in his bag for biotics that worked, but soon realized by the elves that he’d been jerked. For the patient had suffered from MRSA, and the drug is now available… well, that’s a story for another day.”

 

Why is this 2-year-old behind in development?

This 24-month-old reports with developmental delay and drags her right leg. Look at the first four images without arrows, and see what you come up with for a diagnosis. Then, take a look at the next four duplicate images with arrows indicating key findings.

Axial T2 FLAIR

Axial T2 FLAIR

Axial T2 FLAIR

Axial T1

Axial T2 FLAIR

Axial T2 FLAIR

Axial T2 FLAIR

Axial T1

 

Q1 – The diagnosis of lissencephaly (type II) may be associated with which of the following:

(a) Reduction in normal sulcation
(b) Band heterotopia
(c) Neuronal migration disturbance
(d) – (a) and (c)
(e) – (b) and (c)

Q2 (Advanced) – Which syndrome is NOT associated with lissencephaly:

(a) Fukuyama
(b) Cobb’s
(c) Walker-Warburg
(d) Muscle-eye-brain
(e) Miller-Dieker

 

Lissencephaly may be associated with under- or overmigration. Lissos is Greek for “smooth brain”. The defect in neuronal migration occurs in the 12th to 24th week of gestation. Band heterotopias are caused by undermigration. Pebble cortex such as that associated with the Walker-Warburg Fukuyama muscular dystrophy is a form of overmigration. Lissencephaly may be divided into: (a) type I with a smoother, thicker cortex; or (b) type II with a pebbly cortex.

A characteristic of lissencephaly, besides migrational disturbance, is microcephaly. Another classification for lissencephaly is that of the classic (type I) and the cobblestone (type II). Remember that microcephaly plus abnormalities of sulcation and migration suggest lissencephaly syndromes.

Classic (or Type I) lissencephaly is associated with:

Lis I: lissencephaly due to platelet-activating factor acteylhydrolase (PAFAHB1) gene mutation. Subtypes include:

  1. Type I isolated
  2. Miller-Dieker syndrome

Lis XI: lissencephaly due to doublecortin (DCX) gene mutation.

Lissencephaly, type I, isolated without other known genetic defects.

Cobblestone (or Type II) lissencephaly is associated with:

  1. Walker-Warburg syndrome or HARD +/- E syndrome
  2. Fukuyama syndrome
  3. Muscle-eye-brain disease (MEB)

ProScan Pearl: Because of poor gyral and sulcal development, sylvian fissure narrowing, colpocephaly, flat qyri and a thick smooth cortex, lissencephalic brains may demonstrate the “figure of eight sign”.

 

A1 – (d) Reduction in normal sulcation and Neuronal migration disturbance

A2 (Advanced) – (b) Cobb’s syndrome is associated with spine and soft tissue paraspinous AVM.

 

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Reference:

1. Pilz et al. Syndromes with lissencephaly. J Mod Genetics, 1996: 33 (4), 319-323.

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What is the cause of this patient’s weakness and ascending numbness?

This 48-year-old female has indicated lower extremity weakness and numbness. Using image 1, can you identify the abnormality?

Sagittal FSE T2

 

Dural arteriovenous fistula (AVF), the most common spinal vascular malformation, is evident in image 2 (green arrows). There are just too many hypointense “dots”. Dural AVF account for 65% of all vascular malformations of the spine. These are acquired lesions, and 80% of patients are male averaging around 50 years of age. They frequently complain of back and leg pain with progressive myelopathy from venous hypertension, also known as Foix-Alajouanine syndrome or subacute necrotizing myelopathy. This may accelerate or become more pronounced when there is venous occlusion or thrombosis. The point of fistulization (anastomotic fistula formation) is usually near the intervertebral foramen originating from an intradural radiculomeningeal artery and vein. It is a direct connection between arterial : venous side as opposed to the complex tuft or nidus of an arteriovenous malformation (AVM).

Sagittal FSE T2

 

Further imaging findings include (a) serpiginous innumerable filling defects within the subarachnoid space, (b) cord swelling, (c) intramedullary indistinct signal hyperintensity that is contiguous for multiple segments, and (d) mild ill-defined enhancement. Angiographically, either single or multiple feeders from radicular arterial branches are noted. There is usually a single intradural draining vein. A small, yet focal, nidus of arteriovenous shunting is usually noted at the intervertebral foramen.

Unlike many of the other types of arteriovenous malformations, AVFs usually do not present with hemorrhage. The other types of arteriovenous malformations lack a sex predilection (while dAVF of the spine is more common in men), and are likely to present in a younger age. The symptoms of this disease are gradually progressive, unlike multiple sclerosis (a commonly mistaken diagnosis) which is a stuttering waxing and waning syndrome with skip lesions on MRI. If a patient with dAVF (type 1) has a sudden decline, it is usually from venous thrombosis with secondary cord ischemia. This is known as subacute necrotizing myelopathy or Foix-Alajouanine syndrome.

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Reference:

1. Minami et al. Radiology 1988; 169(1): 109-115

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Left-sided tinnitus. No IAC mass. What is the next step in the diagnostic algorithm?

Patient is a 37-year-old with left-sided tinnitus described as buzzing in the left ear. MRI was performed to exclude the possibility of a mass in the internal auditory canal. What are your findings? Try to solve the case with the first three images from the MRI before looking at CT images four and five.

MRI Axial T1

MRI Axial T2

MRI Axial T1

CT Axial

CT Coronal

 

Postcontrast MR imaging demonstrates no evidence of an acoustic neuroma. No vestibular or aqueductal dilation, or confluent otomastoid airspace disease. Additional differential in the setting of buzzing or pulsatile tinnitus could include:

  1. glomus tympanicum
  2. carotid-basilar anastomosis
  3. large glomus jugulare
  4. jugular bulb dehiscence

The diagnosis (jugular bulb dehiscence) was suspected in this case due to the presence of a large ectatic left jugular bulb (images 1-3, green arrows) correlating with the side of described symptoms. The right jugular bulb is indicated with the yellow arrows on images 1 and 3. Followup CT skull base did demonstrate abnormality of the left jugular bulb with deficiency of the left sigmoid plate (image 4, red arrow) with communication between the jugular bulb and the middle ear (image 5, pink arrows). Jugular bulb dehiscence can be a cause of tinnitus and may be suspected when a patulous jugular bulb is present on the side of described clinical interest. Confirmation with skull base CT, as in this instance, can be helpful.

Dr. Stephen Pomeranz

Dr. Malcolm Shupeck

 

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Why is this patient still in pain eight months after surgery?

This 48-year-old male is eight months post surgery for Achilles repair and still has constant pain. You are initially shown three sagittal images and one axial image of the Achilles and repair site without arrows. The first is a fat or T1-weighted (image 1); the second is fat-suppressed or T2-weighted (image 2); the third is sagittal 3D additive gradient-echo / ADAGE (image 3); and the fourth is axial T1 (image 4). What is your differential diagnosis? After thinking about these questions, analyze the same images with arrows (images 5-8).

Sagittal T1 FSE

Sagittal T2 FSE FatSat

Sagittal T2* ADAGE 3D

Axial T1 FSE

Sagittal T1 FSE

Sagittal T2 FSE FatSat

Sagittal T2* ADAGE 3D

Axial T1 FSE

 

The Achilles itself is at least 1.5 times normal anteroposterior thickness with normal thickness being approximately 7-8 millimeters. This increase in size is compatible with prior surgical intervention. However, the internal striations (pink arrows, images 5-7) and hyperintensity seen on the water weighted image are typical of an active hypertrophic tendinopathy, or what we used to call “tendinitis”. Therefore, one explanation for the hind-foot pain is tendon inflammation. Tendons can also enlarge from infiltration as in gout, xanthoma, etc.

A second explanation is that the patient has reacted to the anchors placed in the calcaneus as there is swelling along the superior border of the calcaneus, and possibly between the anchors (lower blue arrow, image 5), which may be in part related to susceptibility artifact and signal distortion. However, a suture reaction was favored clinically, and based on the combination of Achilles swelling, pericalcaneal or subcalcaneal (upper blue arrow, image 5) swelling, and possible intramedullary swelling that is not at all destructive, this is a plausible favored diagnosis by imaging.

The other diagnosis to be considered is infection. Clinically, this should be obvious with draining wounds, erythema, a warm extremity. An experienced clinician usually suspects it. The pattern of marrow edema (usually geographically extensive) and loss of cortical margin, or destruction of bone, is not as prominent as would be expected in somebody with a pyogenic infection, even if such infection were caused by a less virulent form of skin bacteria such as Streptococcus viridans.

Differential diagnosis in descending order of likelihood:

1 – Anchor and/or sutural reaction.

2 – Active tendinopathy with granulation tissue from prior surgery.

3 –  Smoldering infection least or unlikely.

Postscript: The axial T1-weighted sequence (images 4 or 8) with an oval 2 millimeter nidus of intermediate signal intensity. This is the only image on which it was seen. What would you do with it? We have presumed that it represents granulation tissue and have requested a nine-week followup.

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Be sure to make the right differential considerations in this brain case

This 43-year-old female presents with neck pain. Try to work through the case looking at just the first four images, before looking at the same images with arrows indicating key findings.

Q1 – The differential diagnosis includes all of the following, except:

(a) Glomus
(b) Meningioma
(c) Epidermoid
(d) Schwannoma

Axial T2

Axial T1

Axial T1

Coronal T1

Axial T2

Axial T1

Axial T1

Coronal T1

 

A1 – (c) Epidermoid

 

Q2 – Glomus jugulare may present as any of the following, except:

(a) Vernet syndrome
(b) Collet-Sicard syndrome
(c) Horner syndrome
(d) Bell’s palsy

Q3 – Glomus jugulare may demonstrate any of the following, except:

(a) Salt-and-pepper appearance on T1 MRI
(b) Salt-and-pepper appearance on T2 MRI
(c) Minimal or no enhancement on MRI
(d) Erosion of the jugular spine on CT

 

Glomus tumor is a paraganglioma of the jugular fossa which may arise from Jacobson’s nerve or Arnold’s nerve. It may result in cranial neuropathies of the skull base including those in the jugular foramen 9, 10, 11 (Vernet syndrome) or in larger lesions may also involve 12 (Collet-Sicard syndrome). Horner syndrome may also be seen secondary to involvement of autonomics closely associated with the carotid and jugular walls. Bell’s palsy involves the 7th nerve complex which is more superior in location and exits through the internal auditory canal.

Glomus tumor markedly enhances and may erode the jugular spine. The salt-and-pepper appearance due to high vascularity and multiple flow voids in a classic appearance.

It may be part of endocrine adenomatosis IIB/III syndrome and 6-8 percent are multiple.

 

A2 – (d) Bell’s palsy

A3 – (c) Minimal or no enhancement on MRI

 

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References:

1. Eldevik OP et. al. Imaging Findings in Schwannoma of the Jugular Foramen. AJNR 21(6): 1139-1144.

2. Vogl T et. al. Paragangliomas of the Jugular Bulb and Carotid Body. AJR 1989; 153(3): 583-587.

Simple follow-up or important finding?

This 38-year-old male had a seizure 22 years ago. This is a follow-up scan, and the patient has no recent seizures or head trauma. See what you can discern from the first two images before looking at the duplicate images 3 and 4 (with highlighted area on image 4).

Q1 – The finding represents:

(a) Subependymal heterotopia
(b) Giant cell astrocytoma
(c) Neurocytoma
(d) Neurofibromatosis

Axial T2 FLAIR

Axial T2

 

A1 – (a) Subependymal heterotopia

Axial T2

Axial T2

 

Q2 – Subependymal heterotopia can be all of the following, except:

(a) X-linked
(b) Sporadic
(c) Associated with seizures
(d) Focal or diffuse
(e) A manifestation of tuberous sclerosis

Q3 – The following are all true of heterotopias, except:

(a) Can be nodular or diffuse
(b) Most commonly present with seizures
(c) May be associated with agenesis of the corpus callosum
(d) Spectroscopy is usually normal

 

The majority of cases of subependymal heterotopia are sporadic. Some are X-linked. Affected females have mild cognitive deficits. Affected males are spontaneously aborted or have severe deficits. Tuberous sclerosis patients have subependymal nodules, but they are not true heterotopias.

The most common clinical presentation is seizures and developmental delay.

Heterotopias can be diffuse as in this case or focal most commonly in the regions of the trigones or occipital horns.

Differential diagnosis includes tuberous sclerosis. Tubers are usually calcified and have higher T2 signal than normal brain tissue. There are often cutaneous stigmata such as adenoma sebaceum, shagreen patches, or ash leaf spots.

Gray matter heterotopias may be associated with agenesis of the corpus callosum as well as pachygyria, schizencephaly, poly microgyria and Chiari II.

Spectroscopy in grey matter heterotopias demonstrates a decreased NAA/CR ratio, although often mild.

 

A2 – (e) A manifestation of tuberous sclerosis

A3 – (d) Spectroscopy is usually normal

 

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For more neuro case review, check out MRI Online.

References:

1. Barkovich, Radiology 1992: 182, 493-499.

2. Mitchell et. al. Antenatal diagnosis of subependymal heterotopia, AJNR 2000:21 (2).

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