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Some Neuroanatomical Variants usually misinterpreted radiologically


Some Neuroanatomical Variants usually misinterpreted radiologically

Misinterpretation of common anatomical variants can lead to misdiagnosis and unnecessary waste of time and resources. In an era of rapidly progressing technology and radiological studies moving to imaging at a molecular level, sometimes these common imaging features are still confused with pathologies.

It is therefore not surprising that an article entitled ‘’Normal neuroanatomical variants that may be misinterpreted as disease entities’’ has been one of the most popular articles downloaded on clinical radiology within past 90 days (Elsevier).While most can be differentiated on background knowledge of morphology and location, few are still challenging. The most important task is thus, to separate benign, incidental findings so as to prevent overzealous treatment. A brief mention of such mimics is provided in this review article.

ANATOMICAL  VARIANT MAY MIMIC… SOLUTION
Arachnoid granulations Venous sinus thrombosis Usually CSF signal, no blooming on SWI, CT venogram is confirmatory
Developmental sutures eg. metopic Fractures Knowledge of paediatric skull anatomy
Pneumatized anterior clinoid process ICA aneurysm CT bone window, angiography
Asymptomatic pineal cyst Pineocytoma on NECT Follow up
Physiologically enlarged  pituitary Macroadenoma Correlation with age/sex/pregnancy & lactating status
Empty sella Cystic lesion Identification of infundibulum
Developmental venous anomalies Arterio-venous malformatons MRI with SWI, contrast- caput medusa head pattern
Capillary telengectasia- pons Central pontinemyelinolysis,

Pontine Glioma

Contrast MR- faint enhancement, SWI-hypo intense, DWI- no restriction
Hypoplasia of transverse sinus Sinus thrombosis on MRV NECT for small bony groove, routine CECT, MRI with SWI
Prominent Virchow Robin (VR) Spaces Lacunar infarcts, Neuroglial cysts Lacunar infarcts have typical morphology, typical location of VR spaces.
Fossa navicularis magna Lesion in clivus Bone window for erosion, intact clivus
Asymmetric, petrous fatty marrow Cholesterol granuloma on T1 weighted MRI Lack of mass effect, fat supressed images
Petromastoid/subarcuate canal Fracture Knowledge of course of canal

For example when there is confusion in differentiating sinus thrombosis from developmental hypoplasia, the sigmoid and jugular groove in the base of the skull on CT can be looked at. The bony groove will be smaller in hypoplasia. Similarly, for detecting venous sinus thrombus, hyperdensity will usually be seen on CT with empty delta sign on CECT. More definite analysis can be only on contrast venography which can be further confirmed on DSA (with manometry) to evaluate true stenosis.

On MRI, plain T2 images may not show flow void due to slow blood flow. In such case DWI will be useful and SWI will show blooming in the thrombus. The acute thrombus may be missed as it will not be hyperintense on T1/T2 images.

Similar other examples which may mimic pathology-

  • Pcom infundibulum being mistaken for an aneurysm.
  • Hypoplastic ICA can be confused with a dissection or fibromuscular dysplasia.
  • Agenesis of ICA may be confused with occlusion.
  • CT- or MR-Perfusion asymmetry in the occipital lobes, in cases of unilateral fetal PCA. The contralateral side may show delayed perfusion because it is supplied by the posterior circulation.
  • Relative hypoperfusion in the PICA territory in cases of vertebral artery hypoplasia

(Source: http://dx.doi.org/10.1594/ecr2016/C-0199)

 

Abbreviations:

MRI- Magnetic resonance imaging

NECT- Non enhanced Computed Tomography

CECT- Contrast-enhanced CT

SWI-Susceptibility weighted imaging

DWI- Diffusion-weighted imaging

CSF- Cerebrospinal fluid

ICA- Internal carotid artery

 

Source: S. Ramji, P. Touska, P. Rich, A.D. MacKinnon, Normal neuroanatomical variants that may be misinterpreted as disease entities, Clinical Radiology xxx (2017) 1-16

Further reading: Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature by McKinney, Alexander (Springer; 2017)

Dr. Niharika Prasad,

The author is MD (Radiodiagnosis) and is Senior Resident, Dept of Radiology in All India Institute of Medical Sciences, AIIMS Patna. She is a member Editorial Board, Radiology at Specialty Medical Dialogues.

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Anjali Nimesh

Anjali Nimesh

Anjali Nimesh Joined Medical Dialogue as Reporter in 2016. she covers all the medical specialty news in different medical categories. She also covers the Medical guidelines, Medical Journals, rare medical surgeries as well as all the updates in medical filed. She is a graduate from Dr. Bhimrao Ambedkar University. She can be contacted at editorial@medicaldialogues.in Contact no. 011-43720751
Disclaimer: The views expressed in the above article are solely those of the author/agency in his/her private capacity and DO NOT represent the views of Speciality Medical Dialogues.
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