January - February 1999.Lebanese Medical Journal. Volume 47(1) 83

Infantile Spasms on a New Communication Between the
Fourth Ventricle (F.V.) and the Posterior Cyst (P.C.)
other than Dandy -Walker : a New Entity

Introduction: The Etiologies Of West Syndrome Are Usually Categorized As Prenatal , Perinatal And Postnatal. Classic Concepts Of Basic Mechanisms Suggest That Infantile Spasms Are Generated In Subcortical Structures With Ascending Activity Producing Hypsarrhythmia And Descending Activity Producing The Seizures .According To A Newer Concept, Based on The Potential Recovery Following Removal of Cortical Lesions ,The Subcortical Structures Supposedly Producing Hypsarrhythmia And Spasms Are Triggered By Discharges In The Cortical Lesion .Partial Seizure Can Precede, Accompany or Follow The Cluster of Spasms .This Observation As Well As The Asymmetric Spasms Suggest That Cortical "Pace Makers" May Be Important In The Development of "Infantile Spasms". only 10-15% Of Patients With West Syndrome Were Developmentally Normal At The Time of Diagnosis of The Infantile Spasms. In Some Infants With Cryptogenic Infantile Spasms Focal Lesions Can Be Demonstrated Using: Positron Emission Tomography (PET). Surgical Ablations Of Areas Of Hypometabolism On (PET) Resulted In Elimination Of The Seizures. Although The MRI Scans In These Children Were Normal , EEGs And Clinical Seizures Suggest A Focal Onset .

Purpose: This Abstract Aims At Reporting A New West Syndrome Etiology That Consists Of Enlarged Posterior Fossa By A Large Cyst Communicated With A Normal (F.V.) Via Two Separated Canals .

Method: A One -Year -Old -Boy Having Persistent Seizures That Have Started At Fourth Month Of Age As Typical Mixed Infantile Spasms In Clusters .

The Infant Was The Product Of A Full Term Pregnancy -Appropriate For Gestational Age -With Uneventful Prenatal, Perinatal , Postnatal And Family Histories .

His Psychomotor Development Was Doubtful Before Spasms; But Clear Psychomotor Regression Was Noted After The Beginning Of Spasms. weight: 8.5 kgs .Head Circumference =43 cms. He Has Severe Psychomotor Delay With Abnormal Contact , Non Paralytic Axial Hypotonia And Inability To Sit Alone .Characteristically , There Is A Prominent Occiput; No Dysmorphism , Skin Lesions Or Organomegaly .Skull X-Ray Showed Occipital Prominence With Large Posterior Fossa . The EEG Still Showed Fragmented Hypsarrhythmia During Sleep With Prominent Asymmetric Occipital Epileptic Discharges .The Brain CT Scan Showed :Severe Brain Atrophy With Triventricular Dilatation ,Posterior Atrophy Of The Vermis , Normal Fourth Ventricle (F.V.) ,Large Posterior Cyst Communicating With The (F.V.) Via Two Separated Canals .

Discussion: The Present Case Is Distinguishable From Dandy -Walker By:

The Presence Of Very Well Delineated (F.V.).
The Presence Of This Previously Undescribed Type Of Communication Between The (F.V.) And The Posteriour Cyst .
The Occurence Of Infantile Spasms That Has Never Been Described On Dandy -Walker Malformation .

Conclusion: As Subcortical Structures Are Suspected To Be Generators Of Infantile Spasms ,We May Conclude From The Present Case That It Is The Cerebellum, And More Precisely The Vermis ,That Has A Role To Play.