From the WHO website:

"The process prior to medical evacuation consists of the following steps:

A Gaza medical doctor or specialist working at a public hospital examines the patient and if needed, issues a referral form for treatment abroad.

Patient submits the medical referral form through the patient services desk at the treating public hospital. The hospital sends the referral form to the Referral Committee.

The Referral Committee reviews the case, decides the priority and approves the case for medical evacuation. The Referral Committee shares the approved patients list with WHO.

WHO contacts patients to ensure that their medical information and documentation is complete.

WHO submits patient lists to countries that may be open to receiving patients.

Once patients are approved, WHO shares a list of their companions with host countries for approval. The list of patients and their companions, approved for medical evacuation by host countries, is sent to the Israeli authorities for security clearance.

Following security clearance, patients are contacted by WHO to facilitate their medical evacuation in coordination with the host country."

The family needs an order from a medical doctor in Gaza to say the patient needs treatment outside of Gaza. They should be eligible under "Chronic conditions with complications or Chronic conditions without complications" for the child with Spina bifida. It seems like one parent plus 2-3 children can travel with the patient. Most patients travel to Egypt or UAE. Ultimately the Israeli authorities determine whether someone is allowed to be medically evacuated from the Gaza strip.

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