• Diagnosis of CLN2 disease as determined by TPP1 enzyme activity (dried blood spot) in the fibroblasts and leukocytes available at Screening
• Quantitative clinical assessment of the Hamburg motor-language aggregate score 3-6 at Screening on CLN2 disease motor-language scale, as defined in the Ratings Assessment Guideline
• < 18 years of age at the time of informed consent
• Written informed consent from parent or legal guardian and assent form subject, if appropriate
• Males and females who are of reproductive age should practice true abstinence, defined as no sexual activity, during the study and for 6 months after the study has been completed (or withdrawal from the study). If sexually active and not practicing true abstinence, males and females of reproductive age must use a highly effective method of contraception while participating in the study.
• Ability to comply with protocol required assessments (ICV implantation, drug administration, laboratory sample collection, electroencephalogram (EEG), electrocardiogram (ECG),magnetic resonance imaging (MRI), etc.)

Exclusion Criteria:

• Pr

• Presence of another inherited neurological disease, e.g., other forms of CLN or seizures unrelated to CLN2 disease (patients with febrile seizures may be eligible)
• Presence of another neurological illness that may have caused cognitive decline (e.g., trauma, meningitis, hemorrhage) or interference with disease rating (autism) before Screening
• Presence of percutaneous feeding tube placement prior to enrollment
• Has received stem cell, gene therapy, or ERT
• Presence of contraindications for neurosurgery (e.g., congenital heart disease, severe respiratory impairment, or clotting abnormalities)
• Presence of contraindications for MRI scans (e.g., cardiac pacemaker, metal fragment or chip in the eye, aneurysm clip in the brain)
• Episode of generalized motor status epilepticus within 4 weeks before the First Dose visit
• Severe infection (e.g., pneumonia, pyelonephritis, or meningitis) within 4 weeks before the First Dose visit (enrollment may be postponed)
• Presence of ventricular abnormality (hydrocephalus, malformation)
• Presence of ventricular shunt
• Has known hypersensitivity to any of the components of BMN 190
• Has received any investigational mediation within 30 days before the first infusion of study drug or is scheduled to receive any investigational drug other than BMN 190 during the course of the study
• Has a medical condition or extenuating circumstance that, in the opinion of the investigator, might compromise the subject’s ability to comply with the protocol required testing or procedures or compromise the subject’s well being, safety, or clinical interpretability
• Pregnancy any time during the study; a female subject judged by the investigator to be of childbearing potential will be tested for pregnanc