What could be causing tingling in both lower legs, lower arms, and upper back, along with loss of memory, a sensation of feeling in a bubble, and shaking, and how should it be managed?

Urgent Neurological Evaluation Required for Multifocal Paresthesias with Cognitive and Perceptual Changes

Your symptom constellation—bilateral limb tingling, memory loss, feeling "in a bubble," and shaking—demands immediate comprehensive neurological assessment to rule out serious central nervous system pathology, metabolic derangements, or inflammatory conditions.

Immediate Diagnostic Priorities

Red Flag Assessment

Your symptoms raise concern for several urgent conditions that require rapid evaluation:

• Central nervous system involvement: The combination of multifocal paresthesias (both arms and legs), cognitive changes (memory loss), and altered perception ("feeling in a bubble") suggests possible central pathology rather than simple peripheral neuropathy 1, 2
• Stroke or TIA evaluation: Hemibody or multifocal sensory symptoms without clear peripheral pattern require stroke risk assessment within 48 hours 2, 3
• Spinal cord compression: Bilateral lower extremity tingling with upper back involvement could indicate spinal metastases or myelopathy, which requires MRI within 12 hours if neurological deficits are present 4

Critical Physical Examination Findings to Document

Your physician must assess:

• Pattern of sensory loss: Determine if this follows a "glove-and-stocking" distribution (peripheral neuropathy) versus dermatomal (spinal) versus non-anatomic patterns 1, 3
• Motor function: Check for leg weakness, difficulty walking, or legs "giving way"—these indicate urgent spinal cord or neuromuscular pathology 4
• Cognitive testing: Formal assessment of memory, concentration, and orientation using validated instruments to quantify the severity of cognitive impairment 4
• Tremor characterization: Determine if shaking occurs at rest, with action, or specifically when standing (orthostatic tremor) 5, 6, 7
• Gait and balance: Assess for ataxia, wide-based gait, or postural instability that could indicate cerebellar or proprioceptive dysfunction 4

Essential Laboratory and Imaging Workup

First-Tier Laboratory Studies

Order immediately 2, 3:

• Fasting glucose and HbA1c: Diabetes is the most common treatable cause of peripheral neuropathy
• Vitamin B12 level: Deficiency causes both neuropathy and cognitive impairment; critical if you take metformin
• Complete metabolic panel: Assess for renal failure, electrolyte abnormalities, hepatic encephalopathy
• Thyroid function tests: Hypothyroidism causes both neuropathy and cognitive slowing
• Complete blood count: Screen for anemia, infection, or hematologic malignancy

Second-Tier Studies Based on Initial Results

Consider 2, 3:

• Hepatitis C serology: Up to 50% of HCV patients develop peripheral neuropathy
• Serum protein electrophoresis: If monoclonal gammopathy suspected
• Erythrocyte sedimentation rate/C-reactive protein: If vasculitis considered
• Lyme disease testing: Two-tier approach if endemic area exposure 1

Neuroimaging

MRI of brain and full spinal column is indicated given your symptom pattern 4, 1:

• Brain MRI to evaluate for demyelinating disease, stroke, mass lesions, or neurodegenerative changes
• Spinal MRI if any concern for cord compression, particularly with upper back involvement and bilateral lower extremity symptoms

Neurophysiological Testing

Electromyography with nerve conduction studies should be performed to 1, 3:

• Differentiate central versus peripheral causes
• Characterize neuropathy type (axonal versus demyelinating)
• Assess small fiber (pinprick, temperature) versus large fiber (vibration, proprioception) involvement

Differential Diagnosis Framework

Most Likely Metabolic/Toxic Causes

• Diabetic peripheral neuropathy: Most common cause; requires annual screening with 10-g monofilament, vibration testing, and ankle reflexes 2, 3
• Vitamin B12 deficiency: Particularly if on metformin ≥2g daily; causes stocking-glove neuropathy and cognitive impairment 2, 3
• Medication-induced: Review all medications, especially metformin, chemotherapy agents, and statins 2, 3

Neurological Conditions to Exclude

• Multiple sclerosis or demyelinating disease: Multifocal symptoms with cognitive changes warrant consideration 1
• Guillain-Barré syndrome: Ascending paresthesias with potential autonomic dysfunction 1
• Parkinson's spectrum disorders: Tremor with cognitive changes and gait impairment could indicate Lewy body dementia or Parkinson's disease dementia 4
• Spinal cord pathology: Bilateral lower extremity symptoms with upper back involvement 4

Psychiatric/Functional Considerations

The "feeling in a bubble" description resembles:

• Derealization/depersonalization: Can occur with anxiety, depression, or post-concussive syndrome 4
• Pseudosyncope/functional neurological disorder: However, this should be a diagnosis of exclusion only after organic causes ruled out 4

Tremor-Specific Evaluation

Your "shaking" requires characterization 5, 6, 7:

• Orthostatic tremor: High-frequency tremor (13-18 Hz) occurring specifically when standing, relieved by sitting or walking; requires surface EMG for diagnosis
• Essential tremor: Bilateral action tremor, often familial, may involve head/voice
• Parkinsonian tremor: Rest tremor with other motor signs

Management Algorithm

If Metabolic Cause Identified

For diabetic neuropathy 2, 3:

• Optimize glycemic control (HbA1c target 6-7%)—this is the only proven strategy to prevent progression
• First-line symptomatic treatment: Duloxetine 30mg daily for one week, then increase to 60mg daily
• Alternative agents: Pregabalin, gabapentin, or tricyclic antidepressants
• Physical activity improves neuropathy symptoms

For vitamin B12 deficiency 2, 3:

• Vitamin B12 supplementation 2500 mcg daily
• Continue long-term, especially if on metformin

If Inflammatory/Immune-Mediated Cause

For Guillain-Barré syndrome or similar 1:

• Intravenous immunoglobulin or plasma exchange
• Monitor for autonomic dysfunction and respiratory compromise
• Hospitalization required

If Central Nervous System Pathology

For spinal cord compression 4:

• Urgent neurosurgical consultation
• MRI within 12 hours
• Treatment depends on etiology (radiotherapy, surgery, systemic therapy)

For demyelinating disease 1:

• Neurology referral for disease-modifying therapy
• Symptomatic management of neuropathic pain

Symptomatic Management Regardless of Cause

For tremor 5, 6, 7:

• If orthostatic tremor confirmed: Clonazepam 0.5-2.0mg daily (first-line)
• If essential tremor: Propranolol or primidone
• Rolling walker transfers weight from legs to arms and reliably improves gait

For cognitive symptoms 4:

• Formal neuropsychological testing to establish baseline
• Treat underlying cause (B12 deficiency, hypothyroidism, etc.)
• Occupational therapy for safety assessment

For neuropathic pain/paresthesias 3:

• Duloxetine, pregabalin, or gabapentin as first-line
• Avoid opioids due to addiction risk
• Topical capsaicin for localized symptoms

Critical Pitfalls to Avoid

• Do not dismiss as "anxiety" or "stress" without thorough organic workup—the symptom combination warrants comprehensive evaluation 1, 2
• Do not delay imaging if any concern for spinal cord compression or stroke 4, 2
• Do not use acetyl-L-carnitine for neuropathy prevention (harms outweigh benefits) 3
• Do not overlook medication review—metformin, chemotherapy, and statins are common culprits 2, 3
• Do not assume peripheral neuropathy when cognitive and perceptual changes are prominent—central pathology must be excluded 4, 1

Monitoring and Follow-Up

• Regular neurological assessments to monitor symptom progression or resolution 1
• Annual foot examinations with 10-g monofilament testing once neuropathy documented 3
• Repeat cognitive testing if memory impairment persists 4
• Adjustment of treatment based on response and symptom evolution 1

Seek immediate medical attention—ideally through emergency department or urgent neurology consultation—given the multifocal nature of your symptoms with cognitive involvement.